Around where I grew up, Peugeot, Schwinn, Motobecane, and later Panasonic were the top brands, in that order. The couple shops selling Peugeot likely outsold all the others combined here. They were good riding bikes and they were by far the most bang for your buck brand out there back then. The PX10 was king but very few bought them because of the sew-up tires.
The same went for the upper models in the other brands. The U08 was what most bought, mostly because it rivaled the department store bikes price wise. The funny thing is 40-50 years later and no one seems to remember them here. Those who owned them are mostly too old to ride or long gone I suppose.
I've always liked the French bikes for how they ride, but as a big guy, most are simply too short for me. Its the whole knees hitting handlebars thing. I have a 23" Gitane, and a 25" Peugeot and both are on the small side for me when it comes to steering.
I've found, serviced, and flipped a half dozen upper model Peugeot bikes over the years and most seem to sell between $300 and $600, depending on size and condition. Taller frames seem to do best here. If I swap out the rims for clinchers, they sell faster. I tend to be able to sell bare tubular wheels but not bikes with tubular wheels here for some reason.

When it comes to buying bikes, estate sales are hit and miss here, usually when they're done as an auction, bikes go for far less. The real deals are generally at the garage sales, rarely have I spent over $50 for any bike at a garage sale with most being under $20. Some bikes can be that was at the flea market too, road bikes and old three speeds are cheap there, but mountain bikes and BMX bikes sell for top dollar. I suppose its a matter of them knowing the value only on the items they remember personally. In recent years, the better bikes are the cheaper bikes and the Huffy and Kent junk is what sells for more money.
Age has a lot to do with what sells, it seems those in their mid 30's tend to be those who are looking to buy back the toys of their youth now that they have some cash to spend. But most of what they're after now is 90's or 00's era items. A good example is a 1940 Elgin balloon tire bike I just bought for $20. It was in decent enough shape to ride it around for the day at the fleamarket and back to my truck. Condition wise its a 6 out of 10 I wasn't looking for a balloon tire bike but for $20, I was pretty much forced to take it home with me.