When creating a subscription, I select a price for it, but I can only select, I cannot say exactly how much my subscription will be. Example, I selected a value of $ 2.99, but I wanted it to be $ 2.70 and that value does not exist in the list of values.
Is there a way to say what the value is specifically for my subscription?
No that is not possible. You can only use the Tiers that Apple provide.