The most I have ever paid for a dish is $20 and that was for a 10 foot Channel Master in really nice shape. As others have said about half the time people want them out of their yards. In a couple of instances I have left a note on the door and months later got a call from someone who decided they just wanted that dish gone. And nobody's ever insisted I dig up the pole or fix their lawn!
The problem with smaller dishes is that even if they work well now, that doesn't mean they always will. I've got a 7½ footer that for YEARS has been reliable on Galaxy 16 (it was my second C-band dish) and prior to that I had used it on the Alaska channels before they were scrambled. Toward the end of last summer it stopped working on both the PR and MO muxes. Changed to a 10 foot C-band dish to receive Galaxy 16 and got everything again. No idea if the satellite got a bit weaker, my LNB started giving out (it's a dual output LNB and if something went bad it affected both outputs), or what happened but the point is that with a smaller dish you don't have a lot of headroom. If I had a six footer I'd probably put a Ku LNB on it and point it at SES-3, since I have problems on that one even with a 4 foot dish, but I can pretty much say that for all but the strongest signals you will be likely be disappointed with the performance of a six footer on C-band.
Best one I saw was a woman that had a nice looking 10 footer in her yard, only it was up on a very tall pole (in my area one of the satellite installers also had a tree service, so they used to love to convince people to pay extra for the tall pole which they'd install using one of their bucket trucks, and a lot of those are still around because no one can get them down safely without hiring a bucket truck or crane, which most people won't do). I had no idea how I would get it down but when I asked her about it, she said "I want $100 for it! I know what those dishes are worth, I'm not going to give it away!" Well, okay then. I told her I'd think about it. That was a couple years ago and I'm still thinking.
The only way she's ever going to get that out of her yard is if someone a lot more desperate than I is willing to hire a bucket truck or crane, or if she takes a Sawzall to the pole and just cuts it down, which would damage the dish irreparably (and if she doesn't know what she's doing she'll drop it on her garage or house, or maybe herself). Either way, there's a lot lower hanging
fruit dishes still around!