For flash the input/output is the same, but the cache difference is big, you're paying 10x on >95% of your tokens.
For Pro, it's even worse, input/output is 4x and cache is 40x. The price different is really brutal. Yes you will still come out ahead by spending your first 10$/month on opencode go, but you will be saving a lot less than initially appears from their (60 USD for 10 USD pitch).