Just yesterday I saw a pair of Sennheiser wired ear buds on USAM and the seller quoted a retail price. He was asking was 50% of that price. Naturally, I quickly and painlessly looked these up on Amazon and a dedicated audio retailer and found the actual retail price to be substantially lower than the seller indicated. I was considering making an offer for these earbuds but not after I caught him inflating the supposed retail price. BTW, I consider the retail price to be the actual price you would pay for a brand new unit under full warranty from an authorized retail channel. For older models that are out of production I use whatever the reviews say was the retail price at the time of the review.
I've got a simple piece of advice for sellers. When you inflate the retail price of your item it just makes you look dishonest and stupid. It only takes a few keystrokes to find out the true retail price.