I’m just armchair quarterbacking here but I feel like you should just do all features for every user with a single $/action rate, then give discounts for volume and/or prepayment. Even saying $20/200 is a clunky statement. You could just say $0.10 per action (the fact that you’re actually requiring me to make a $20 payment with a $20 charge once it gets to $10 or something like that isn’t even important to me on a pricing page, although when you mention it later in the billing page make sure you also tell people it’s a risk-free money back guarantee if that’s the case)

If there’s something that truly has an incremental cost to you, like providing priority support, that goes into the “enterprise pricing” section and you need to figure out how to quote that separately from the service. My guess is most people don’t want to pay extra for that, or perhaps they’d pay for some upfront integration support but ongoing support is not too important to them. Idk, that’s just my guess here.

thanks - definitely worth saying - I've thought a bit about the 10c/operation rather than 200/$20 - might give that a shot or A/B test a little