You guys are funny. If you want full value for your products then sell it on CL, eBay or Amazon. Simple as that. For the majority of the people that aren't savvy or do not want to deal with the BS then there's the trade-in programs which simplify everything for a cost. Of course you're not going to get top dollar! They are businesses. It's a given you're only going to get a portion of the value. They will obviously account for the business costs and profit into it. To think otherwise is just stupid. Since when do you get BlueBook Value when you trade in your car at the dealership?!
I've dealt with a few of these trade-in programs before. True, I could have made more selling it myself (which I prefer to do.) But did it save hassle, yes. Was the lower trade value make up for less hassle? Not for me but maybe for others. They send you a box with a prepaid label. You send it in, they give you a value. You either accept or decline. If you decline then they send it back to you free of charge. YOU have the choice. I don't see a scam there at all.