The current realistic lower bound for actual work is the $100/€90/month Claude Max ("5x") plan. It allows roughly enough usage for a typical working month (4.25 x 40-50h). "Single-threaded", interactive usage with normal human breaks, sort of.

There are two usage quota windows to be aware of: 5h and 7d. I use https://github.com/richhickson/claudecodeusage (Mac) to keep track of the status. It shows green/yellow/red and a percentage in the menu bar.