DirecTV and Dish both abandon their dishes when they lose a customer. It's not worth it to them to send someone out to retrieve it, and if they remove both the dish and the "J pipe" mount, they would have to patch the roof (it's screwed in). Plus, it's free advertising for them as long as it remains there.
So, it's worth nothing to the satellite companies. It's too small for other uses, although several people have used the larger ones (the "slimline" or "world direct" models) for Free-To-Air satellite. But there are a lot of them available free, so nobody's going to pay you for one.
I would suggest you either leave it there, or remove just the dish and leave the mount - to keep your roof from leaking - unless you want to patch the holes left behind. You can take the dish to your recycle center (it's aluminum, about 40 cents a pound), or make it into a dandy birdbath or bird feeder.
If you're really looking to make a buck off it, remove the dish, leave the mount, attach an antenna to it, hook it up to the cabling DirecTV installed, and get FREE HD TV. In most locations you can get 20-40 channels free. That's a savings of $70 a month over the average cable bill, amounting to a tidy sum of more than $8000 over 10 years. We can help you with that, just ask.