It looks to be in OK shape....not minty fresh but I'd still leave it as a dedicated game. There are plenty of beater/generic cabs to hack up for MAME use. Ms Pacs will always have resale value, so I'd have it tuned up and enjoy it for what it is.
As for a price, I dunno. It really depends on what its worth to you. If its been sitting for many years and likely needs some work (does the pix on the monitor look bright, full and focused or is it washed out with caved in edges or foldover?) I'd not go over 300$.
Anyone buying a classic game that's not been restored needs to remember that its now 30 or more years old and if its not been serviced it *will* need to be. Since they were not intended to last that long to begin with, anything that is bone stock is on borrowed time at best......