I enjoy going to the Electronics Flea Market myself, but I must be getting up too late in the morning because I've yet to walk home with anything particularly interesting in the "vintage computing" category. (I did come home with a couple free TRS-80 keyboards from a guy that scrapped a pile of them and discovered it actually wasn't that easy to sell off the parts. Insert eyeroll emoticon here. I also have a Tandy Model 100 portable that came with all the manuals and a softcover for $20, but I didn't actually spot that, a friend who *was* able to get his butt out of bed at the crack of dawn picked it up for me.)
When it comes to Apple stuff in particular it seems like a lot of the vendors suffer from "I saw one of these at this price listed on eBay so obviously that's what it's worth-itis"; you'll see things like Apple IIe's with missing keys and ripped Disk][ cables priced at $75 and DuoDisks with dirty cracked cases for $50. And if you ask them to dicker you'll find that they're very attached to their wishing prices.
Ironically perhaps I've had a lot more luck finding oddball non-computer related collectables there. For instance, I traded a fiver for a really nice condition
November 29th, 1963 issue of Life Magazine. Also found a really neat old electronics learning kit from the early 1960s that uses telephone-style banana jack cables and has an awesome folding steel case for only like $10. The cables and instructions were missing but it's still awesome; we use it as a Halloween mad science prop.
