You have to be more specific:
1. Brand New/sealed/STILL IN PRODUCTION?
2. Brand New/not sealed, but never used/ STILL IN PRODUCITON?
3. Brand New/sealed/old stock/NO LONGER IN PRODUCTION?
4. Brand New/NOT sealed/old stock/NO LONGER IN PRODUCTION?
You get the idea.
In regards to pricing, it can be all over the place, as some sellers are just need the cash/ditching it ASAP, others are resellers (trying to make a profit), etc.
Buyer's NO LONGER care about the retail value/MSRP. Why you ask? Simple, I can easliy (any given time) buy BestBuy giftcards for 60% of their value, which means that I already get a 40% discount. Now, befriend a BestbBuy employee and save even more money with the employee discount. Don't even get me started on the potential savings that can be had at Fry's Electronics, if you know the right people (all done legally).
If you want the simple answer, get the averge "sold" price from eBay and lower it another 10%. IMO, most of these apps are AFTER eBay "garage sales"