Yeah, no surprise there. I'm not trying to beat a dead horse but there are just way too many awesome aftermarket rims that can be had for under a grand to spend that kind of money on some OEM take-offs.
Like selling anything, I guess you just have to ask yourself how bad you actually want to sell them. If you really want to hold onto them, and don't mind 4 big ol 20" rims and tires sitting in the garage, then ask top dollar and hope that the one lone buyer who is willing to drop major bucks finds you. If however, you'd rather have the cash, mark em at a reasonable price lots of people will want to jump on and you'll have them sold in no time.
As for holding onto them so you can put them back on later if/when you sell the truck, that's an ok idea in concept. I buy and sell a lot of motorcycles, and with those I do typically hold onto stock parts. Why? Because aftermarket upgrades rarely recoup much of their cost and often don't help sell a bike. Clean, stock bikes often attract more buyers. I'll put the stock parts back on when I go to sell the bikes and sell off all the aftermarket goodies for 2/3rds of what I have in them. Not bad. But I sell frequently and don't hold onto the bikes for a long time. So now let's investigate the idea with truck wheels and tires.
How long do you plan to own your truck? If you're like jasonjl85 and you're likely to sell or trade your truck in a year or two it may make sense. If you plan to hold onto it for 4-7 years what are you going to do when you sell it - put 4-7 year old tires back on the truck? What are the chances you're next vehicle is going to have the same bolt pattern, lift, etc to run your aftermarket wheels you just pulled off? And even if you wanted to sell the aftermarket wheels because you think they're worth more, are they really going to net you that much return when they've been used for 4-7 years. I'm not saying these are out of the question, but just some things to think about to determine the real probability of going this route.
And probably the biggest factor in my mind - If we were talking about selling the wheels and tires for a few hundred bucks the sale would barely put a dent in the price of the new wheels and tires. But recouping say $500-600 on the wheels alone would cover as much as 50-60% of the upcoming purchase. Sure, $1,000 for the wheels would cover more of your next purchase, but again you have to wonder if you'll be patient enough to find the guy willing to pay that kind of money.
Anyway, I don't have any stake in the game but I think about these things a lot because I buy and sell a lot vehicles, and thinking through the best options is part of the fun for me.