Can I ask how you host your emails? I have a similar situation but the price for most hosts for a wild-card domain is prohibitive.
Almost every email host that supports custom domains supports receiving email with unlimited wild-cards. Is there something I'm missing?
Example: https://www.fastmail.com/pricing/ ($3/month)
I'm also fairly sure that they don't let you reply as the address the catch-all was placed on, which is an important feature.
If you know any that do, that'd be great.
The point still stands though, if you have a mail provider that supports custom domains there usually isn't a limit on the catch all aliases you can add (or a very high one). In any case it's far from being "prohibitively" expensive.
> I'm also fairly sure that they don't let you reply as the address the catch-all was placed on
That is definitely possible with Fastmail as that's how I use it. In their case I believe that feature is called "Alias". If you reply to an email you just select with alias you want to reply from.
I know this is not available any more so I've done the same with Cloudflare Email Routing which lets you set up a catch-all and is (still) free.