> First of all, there's no dollar amount tied to how many credits you get for a subscription.

I don't understand what you mean here; their official comms is:

     Customers on existing Plus, Pro and Enterprise/Edu plans should continue to use the legacy rate card. We’ll migrate you to the new rates in the upcoming weeks.

To me, anyway, that means that GP was exactly right - they'll give the $20 subscriptions $20 worth of credits, and the $200 dollars subscriptions $200 worth of credits. That is what the "New Rates" are!

I think it would be more rational to discount a subscription (standard is about 10% in most industries) vs PAYG and agree in principal with your assertion - they haven't specified what the discount is on credits bought in a subscription plan - but there is no indication that they are going to continue allowing thousands of dollars of credits on a $200/m plan.

My guess would be a 10% (or similar) discount if you buy a subscription.