Cost deltas

Read this first: the estimate is order-of-magnitude and is never a billing source of truth. It exists to tell you a change adds roughly $40 a month rather than roughly $4,000. If you need a number you can put in a budget, get it from your provider.

With that stated, here is what it does.

What gets priced

Costs are computed over parser facts — the literal values in your code. A resource whose shape Garboard recognises contributes its estimated monthly cost; the delta is the difference between the pull request and its base.

What is unpriced, and why that is not zero

Two cases are reported as unpriced rather than counted as 0:

• Variable-driven values. An instance size that comes from var.db_size is not a literal, so it is not priced.
• Unknown shapes. A resource type or size the table does not know contributes nothing and marks the estimate as partial.

The distinction matters more than the arithmetic. “This change costs nothing” and “we could not price this change” are completely different sentences, and collapsing them into $0 is the kind of quiet wrongness that makes people stop believing a number. A partial estimate can block if what it did price crosses your threshold, but it never clears — an unpriced change is not a cheap change.

When it comments

A priced monthly increase at or above cost.comment_above_usd comments on its own, even when the pull request is otherwise clean. The default is 0, meaning every priced increase says so.

It renders as a context blockquote: no severity, never one of the three finding slots. It is telling you something, not judging you. See when Garboard says nothing.

Where the threshold lives

cost.comment_above_usd is an organisation policy setting. Set it higher to hear only about material increases; set it to a large number to switch the signal off.