In my experience it's about $10 USD to get the first MKStack prompt completed with Claude Sonnet 4. After that, it depends a lot on what you are trying to do. For a super simple app you could probably get an MVP in ~$100. For a more detailed client that does a lot of things, easily you could spend $2,000+ on Claude.

It's a balancing act. Because, on one hand, how much would it cost to hire a human to do it? Or, how much is your own time worth to you?

You do start to get a sense of what tasks are worth vibing and which are not. Ex. If I know it would take me less than a couple minutes to just do it myself, I ususally do. You can also consider swapping agents for tasks that are simpler (stacks agent -m gemini-2.5-pro-preview). However, IMO Gemini is pretty stupid with code compared to Claude - so even if its cheaper if it takes more than two tries it might do more damage than it's worth.

Good prompting also helps reduce the amount you spend on fixing errors or miscommunications - and that takes practice.

Just my experience! Depends heavily on your final goal :)