Tear down per-unit or per-customer economics to find out if growth is actually making money or just making revenue

You are tearing down the unit economics of one customer or one unit of the offering described below — the goal is finding out whether each additional customer is genuinely profitable on a fully-loaded basis, not just contributing revenue that looks good until the fixed costs it's actually eating into get counted somewhere else.

WHAT ONE "UNIT" IS
One subscribing customer on the standard monthly plan.

REVENUE PER UNIT
$49/month recurring, plus a one-time $99 onboarding fee at signup.

COSTS I'VE ALREADY IDENTIFIED AS VARIABLE
Cloud hosting cost per active user ($3.20/month), payment processing fees (2.9% + $0.30 per transaction).

COSTS THAT MIGHT BE PARTIALLY VARIABLE
Customer support staffing — currently 1 support rep per roughly 250 customers; and a shared data pipeline cost that increases in server-cluster increments.

GO THROUGH THIS SEQUENCE:
1. Confirm which of the identified variable costs are genuinely variable (scale directly with each additional unit) versus actually step-fixed (only increase in chunks, like needing to hire one more support person per 200 customers rather than a smooth per-customer cost) — a step-fixed cost misclassified as fully variable understates true unit economics at the margin right before the next step.
2. For each ambiguous cost listed, make a specific call: genuinely variable, step-fixed, or fixed, and state the reasoning in one line rather than leaving it unresolved.
3. Calculate contribution margin per unit using only the costs confirmed as genuinely variable, then separately show what the margin looks like if the step-fixed costs are averaged in at current volume — label this second number clearly as volume-dependent, since it will look worse as volume approaches the next step threshold.
4. Flag if the revenue-per-unit figure includes any one-time revenue (a setup fee, an upfront payment) that won't recur — blending one-time and recurring revenue into a single per-unit figure overstates the ongoing economics.

Do not conclude whether the business overall is profitable — this is a per-unit teardown, and overall profitability also depends on fixed costs and volume that aren't part of this specific calculation. State that boundary explicitly.

OUTPUT FORMAT
1. Cost classification table: cost | genuinely variable / step-fixed / fixed | reasoning.
2. Contribution margin per unit (variable costs only) and the volume-adjusted margin (including step-fixed costs at current volume).
3. One-time revenue flag, if applicable.
4. Explicit statement that this doesn't determine overall business profitability on its own.