Should I buy this 16mm projector/lot?

Maybe. If you know how to run it and want to have a bit of fun watching old 16mm movies. Not really sure what use it will be though other than some kind of collectors item.

edit:
by collectors item, i mean importance to you - more like a cool memorabilia, rather than collectors in terms of monetary value. Just FYI, in case you're thinking you might one day make millions...

I'm not sure what you mean by "in the know". I don't think too many
people here know your interests. If you want to own a 16mm projector,
speaker and 5 old westerns, then this is worth it. It's not a collectable,
if that's what you mean - that's why the entire package is so inexpensive.
But it's fun to watch old movies projected on a screen. I own a 16mm
projector and 18 films. This is a great buy if it's something you want to own.

Remember to get a screen.

You never know what you can get in an odd lot sale. Sometimes it's good and sometimes it's a box of junk. Recently I bought an odd lot from ebay. I mainly bought it for the Moviola film cranks that were the main item in the lot. There was also a Bell & Howell projector, six split reels and a few empty cans for 125.00. When it came the cranks were in good shape, the projector worked but the take up reel would skip, reels and cans were ok but at the bottom of the box I found a Dr. Leo Catozzo M2 16mm tape splicer in perfect condition. It was like finding a gold nugget.

I don't know if the lot you're looking at has a gold nugget, it's a risk. I'm more curious what's on the film reels. Good luck to you.