AI Sandbox Pricing at Scale: $7,200 vs $16,819 vs $24,491 vs $35,000 for 200 Sandboxes

Five vendors sell what they all call the same thing: a secure, ephemeral sandbox where an AI agent can run untrusted code. Price out 200 of those sandboxes, running the same workload, for a month, and the bill ranges from $7,200 to more than $35,000 — a five-fold spread for a commodity the entire pitch deck says is interchangeable. That number comes from a 2026 benchmark Northflank published comparing itself against E2B, Daytona, Modal, and Fly.io Sprites; the gap isn't a rounding error, it's the difference between billing models that meter fundamentally different things.

This post does two things. First, it lays out the actual per-vendor numbers and where the spread comes from — idle-time billing, per-core versus per-vCPU metering, and the managed-platform markup. Second, because the source benchmark is published by the cheapest vendor in the comparison, it independently reconstructs what the same 200-sandbox workload costs bin-packed onto hardware you rent or own outright, using real post-price-hike 2026 Hetzner rates rather than repeating anyone's marketing number.

The Numbers: One Workload, Five Vendors​

Here's Northflank's published comparison for 200 concurrent sandboxes running continuously for a month, priced on an nf-compute-100-4 plan hosted on an m7i.2xlarge node:

A caveat worth stating up front: this aggregate table comes from Northflank's own blog, and Northflank is the vendor that comes out cheapest on every row. That's a real conflict of interest, so before trusting the comparison, it's worth checking the piece that actually drives it — the underlying per-unit billing rate — against each vendor's own pricing page rather than Northflank's arithmetic:

Those unit rates check out independently — they match what each vendor publishes on its own site, not just what Northflank says they charge. The $7,200-versus-$35,770 aggregate is real arithmetic on real rate cards. What's Northflank-flavored is the framing of which vendor comes out on top, which is exactly why the rest of this post rebuilds the self-hosted comparison from scratch instead of quoting Northflank's BYOC figure directly.

Where the 4x+ Spread Actually Comes From​

Three mechanisms account for almost all of the gap between $7,200 and $35,770, and none of them is "one platform is better engineered than another."

Idle-time billing is the single biggest lever. Fly.io Sprites bills per-second "active CPU" and charges nothing while a sandbox sits idle with its filesystem preserved — a genuinely useful property for agent workloads that spend most of their life waiting on a model response. But Fly.io's headline rate ($0.07/CPU-hr) is already 39% higher than E2B and Daytona's ($0.0504/vCPU-hr) before you factor in that Northflank's benchmark assumes sandboxes running continuously, which is the one usage pattern where "billed only when active" provides zero benefit and the higher headline rate is all that's left. A workload with genuine idle gaps would narrow this gap considerably; a workload that's always-on, as modeled here, doesn't.

Per-core versus per-vCPU metering hides Modal's real price. Modal advertises $0.1419 per physical core-hour, which sounds competitive against E2B's $0.0504 per vCPU-hour until you remember Modal's physical core equals two vCPUs. Normalized to the same unit, Modal's rate is $0.071/vCPU-hr — 41% more expensive than E2B or Daytona, not cheaper. The headline number uses a bigger unit to make a higher price look lower; it's the same trick as quoting a car's cost per axle instead of per wheel.

BYOC versus fully-managed is the largest single line item. Northflank's own PaaS ($7,200) versus its own BYOC option ($2,060) for the identical workload is a 3.5x difference — and that's the same company's infrastructure, the same runtime, the same isolation model. The only thing that changes is who owns the compute and who collects the platform margin on top of it. That gap is the honest size of "fully managed" as a line item, independent of which vendor is selling it.

What 200 Sandboxes Cost on Your Own Hetzner Boxes​

Here's where Northflank's own BYOC number gets set aside in favor of an independent build from current hardware pricing — because "self-hosting is cheaper" is worth checking against real numbers, not asserted.

Hetzner tripled the price of its dedicated-vCPU CCX line on June 15, 2026, blamed on a 43–48% quarterly spike in DRAM contract prices. A CCX33 (8 dedicated vCPUs, 32GB RAM) went from €62.49/month to €138.49/month — a 122% increase. At the current EUR/USD rate (~1.14), that's about $157.88/month, or $0.2163/hour per node.

Divided flat across 8 vCPUs with no packing optimization at all, that's $0.027/vCPU-hr — which, notably, is already more expensive per vCPU than Northflank's negotiated PaaS rate ($0.01667/vCPU-hr). Self-hosting is not automatically cheaper than a well-negotiated managed platform just because you own the box; Hetzner's 2026 price hikes narrowed that gap specifically, and pretending otherwise would be the cherry-picked version of this argument.

The real advantage shows up once sandboxes are packed by guaranteed resources with burst headroom, rather than reserved 1-to-1 — the same technique Northflank's own BYOC pricing uses (a published "request modifier" of 0.2, meaning each sandbox guarantees 20% of its plan size and bursts to the rest when the node has spare capacity). Assume a 1 vCPU / 2GB sandbox — a lightweight default in line with the smaller end of E2B and Daytona's own templates — and reserve about 15% of each CCX33 node for the container runtime's isolation layer (gVisor or Kata) and cluster overhead, leaving roughly 6.8 of 8 vCPUs allocatable:

That range is the honest answer, not a single number. Naive, no-burst packing on owned hardware already undercuts every fully-managed vendor in the comparison, including Northflank's own PaaS tier — but only by about a quarter, because reserving a full vCPU and 2GB per sandbox wastes most of a node's RAM once CPU becomes the binding constraint. The real gains — the ones that make owned hardware cheaper than any vendor's BYOC price, not just its PaaS price — come from applying the same oversubscription ratio a managed platform already uses on its own infrastructure. At 5x, six CCX33 nodes running 200 sandboxes lands at $947/month, under half of Northflank's own $2,060 BYOC figure for the identical workload, on hardware that's already 122% more expensive per vCPU than it was before Hetzner's June 2026 price hike.

The Real Lesson: Bin-Packing Changes Who You Benchmark Against​

The Kubernetes project shipped an official Agent Sandbox primitive on March 20, 2026 — gVisor-isolated, warm-pool-backed sandbox CRDs built on existing pod and RuntimeClass primitives rather than a bespoke microVM control plane. GKE's implementation saw more than 16x growth in sandbox usage in under five months, with LangChain and Lovable running production workloads on it. The significance isn't the specific CRD; it's that "run untrusted agent code, packed efficiently, with burst headroom" is becoming a standard cluster-level pattern instead of a proprietary sandbox vendor's pricing trick.

That matters for the buy-versus-build calculus. A platform that already owns Cluster-API-managed hardware isn't choosing between "build a sandbox service" and "integrate E2B" — it's choosing between paying someone else's fully-managed markup and applying the same oversubscription math that platform already runs, on capacity it already owns. The benchmark that actually matters for that kind of platform was never the $35,770 Fly.io number or even the $7,200 Northflank PaaS number; it's whether a well-packed owned-hardware fleet beats a well-packed BYOC fleet, and by how much.

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Sources:

• AI Sandbox pricing comparison (2026) — Northflank blog
• Pricing — E2B
• Pricing — Modal
• Pricing — Fly.io
• Hetzner Price Adjustment 15 June 2026 — Hetzner docs
• Running Agents on Kubernetes with Agent Sandbox — Kubernetes blog