I currently have two MacBooks, and I'm trying to sell one of them. Long story short, I bought the rMBP on Black Friday, sort of regretted buying it (though it is a sweet machine, but expensive), but I'll decide on which one to keep based on which one sells.
The 13" Retina MacBook Pro is in like new condition. This is the base model, but with a 256GB SSD upgrade. It has been opened, but only used for a few days, and everything is basically new. The shrink wrap is still carefully covering the box! Comes with original box, charger, etc... Will have a fresh install of Mountain Lion.
The MacBook Air is in perfect condition functionally and cosmetically. Super fast performance and plenty of storage with the Aura Express Pro 360GB SSD upgrade ($500 retail). This MBA also has the upgraded memory to 4GB SDRAM. Battery life is as good as new (around 100 cycles). Comes with original box, charger, paperwork, etc... I will put a fresh install of Mountain Lion also.
I'm trying to sell the rMBP for $1700 (which is $300 off retail), or the MBA for $1100. Add $12 for Standard shipping or, $20 for Priority Mail 2-3 day shipping. I can take Paypal if you'll cover the transaction fee.
Feel free to check out my eBay feedback (gametime10). I also have these machines listed on eBay under that account if you want to see some pictures. Email me if you're interested - gametime [at] gmail dot com.