Man, that would have pretty danged tempting had I seen it under the same circumstances. But I probably would have dragged some gear over there (if they were cool with that) and hooked it up. That little plastic cover for the side car is so hard to find... Personally I think $150 is too high for an unknown quantity without a keyboard, though.
I'll put it this way. I've bought an A1000 in "perfect" condition visually, with a functional keyboard but without RAM, and spent $200 on that. Granted it came with a lot of disks and an external FDD and a few other odds and ends. But I found out later that the motherboard was indeed dead, unfortunately, and it had no front expansion RAM. Buyer beware.
But at home I had a really nasty looking A1000, yet it worked absolutely perfectly. I wound up gutting the working machine and putting it into the visually perfect (but dead) machine's case. I then had what looked and acted (and is) like a mint A1000.
I did have two keyboards now...
I'd offer them $100 cash. If you can't source a keyboard, I'll pay for the shipping.
or the kickstart/workbench disks
Even if you just hooked it up to a monitor via composite, you should get the Kickstart request screen in crappy black and white assuming the MB isn't toast. You don't need disks to see if the MB is alive or not. If you got to that screen, the only real unknown at that stage would be if the FDD worked or not.
If you did snag it for $100 and it still didn't work, all you'd need to wait for is a butt ugly one that does work and do the swap-a-roo. Man... too bad it doesn't have a keyboard.
FWIW the original mouse is not easy to find in good condition. But it can use any Amiga mouse until you source one.