A full stack developer is either a back end developer that has no business writing front end code but does it anyway, or they’re a front end developer that has no business writing back end code but does it anyway.
Or they’re perfectly capable of doing both because they’re at a startup that’s years away from running at scale or having to worry about performance and security.
It’s not monthly. They bill per blink. A la carte blinkers are so hot right now.