A machine to wash build plates?

[Eponymous]

Washing glue off build plates is for losers.

Is there a machine that does this?

If there is not, who would buy one?

[CincinnatiDesigns]

Like a dishwasher?

Most buildplate glues are water soluable. Just takes some warm water for a few seconds.

[RetroSharky]

Camping dishwasher. You can also use it for circuit boards. But: You have to make sure to use the right cleaning agent - not the harsh stuff - and definitely not regular dish soap - that would create a bubble bath in the whole place. I made that mistake once in my life, and never again.