I remember a pobox faq back then to the effect of "how do I know you'll still be around?" IIRC it asked, rhetorically, how do you know your bank will still be around?
Well guess what? New Brunswick Savings Bank got swallowed up by bigger and bigger players since then. But pobox has stayed the same. It's been so reliably the same I haven't even bothered to get a vanity domain.
I did once use FastMail too but their circa-2007 web interface was too clunky and I dropped them for that one that reads your emails...
I'm curious what's making it expensive.
For what it's worth, I'm on the Enhanced $40/year plan and I use it for personal email as well as side projects.
I just setup a new virtual domain, a new profile, and a rule to move all mail addressed to that domain to a folder for that project.