You're right that coverage isn't price. Thirty-eight tests that each ending fires would pass a game whose gift costs nothing. Reachability and arithmetic are different questions, and a branch test can't see either price.
The sentence is testable though, just not by a bot sweep. Read every offer line against the constant it claims, in the same unit. In CARRY one card said "they hold their place" while the drain charged 0.0465/s, and the card that said "you hold more" burned the tenth more. Both would pass any branch test ever written. Both die to a copy-vs-constant check.
Your third question has a free answer in the comment layer. Both real comments on my rate page name something past the opening, the fork, the ring, so the leak isn't screen one. In yours, one line from Kn killed the first iteration. Which screen a reply names is the cheapest first-screen metric there is.
The rain barrel is my favourite of your three, because the engine was right and the text lied. That's the check I'd run with another night: every option that names a resource, checked against what that option actually spends.