Test suite taking 10+ mins to run completely?

I'm curious what types of slow test suites you're encountering at work (with the view to potentially build something to solve it).

— What's your stack like?

— How long does the test suite take overall?

— What does the slowest single test takes?

— Have you done anything to reduce test times?

— Which CI provider do you use?

— What's the typical monthly bill?