Legends Ultimate is $600 with a monthly subscription to play games, or the choice to buy the games to download locally, as well as a few hours to play any unsupported game each month.
A1Up is $50 on clearance, then you buy a Pi 4 kit on Amazon for $80. Nobody is spending $415 for the Star Wars cabinet and then modding it from there. You still have two working units that can be played separately, with the Pi 4 being a really great mini-console if you decide you don't like the arcade setup.
You're right, it's for people who wanted one but don't want to invest $600, or buy a subscription, or buy individual roms, or allocate more area for a full-sized cabinet. I don't have friends who'd see any man-cave arcade as anything more than a novelty they might play for a few minutes before going back to X1/PS4/N64.
I spent $450 shipped from Sams (and $20 on a low profile 128gb usb3 drive). The machine is full size height with a slim depth profile that sits nicely in my home office while having a fairly significant collection of games to play sourced from a google drove on reddit.
The control panel is decent, lighted marquee, 24” monitor, and the artwork is tolerable. There is no comparison between this and A1up modded into a multicade...the A1up is a poor value proposition for a mame cabinet imo