You can build for a lot cheaper, but again, you need to be honest with your own level of capability (design/ carpentry/ computer and software) and amount of time.
Looks like the build that is quoted is for a two player... do you want 2 or 4? spinner? track ball? light guns? you can go crazy with this stuff.
All the software is "free" online. I've designed and built a mame pedestal cabinet and have both a hyperspin and launch box/ big box set ups. 4 player, spinner, trackball, a separate 4 way joystick for retro games. More than happy to go through the process with you.
Again, to build it's a hobby. If you want a "turn key", you'll just have to decide what you want and how much you are willing to spend.
The software definitely has some hiccups in it. I like that the person you received the quote from is offering support.
Again, more than happy to help support the community. let me know how I can help!