I've sold a few items on bitmit - and looking back, I think I could have priced these (very few) items at about 50% of the price I bought them at wholesale and still made a profit (due to the current year long rally).
"Looking back" being the key. There are many commodities, shares, and so on, of which this could be said, but it only makes sense when doing a transaction to consider the current price.
Look at it this way. You could have sold your items priced in Dollars, and then purchased Bitcoins straight away with your Dollars. So it is also true that you could have priced them in Dollars at 50% of the price, and still made a profit, still due to the current year long Bitcoin rally.
In other words, you should consider these things separately: selling something for its current value, and investing value over time so that it grows.
I purchase wholesale items for about 90c from China and then sell them for 4 or 5 dollars - ie the value of these items to me is 90c.
I want to make a profit, but I also want to attract bitcoin buyers, so I can offer bitcoin buyers a cheaper price. I have no credit card fees or paypal fees or chargebacks with bitcoins, so I can cut the price; and I also want bitcoins, so I can cut the price further.
The value of something someone sells in Bitcoins does not need to be the same as the dollar price unless they are doing a currency exchange (for amazon gift cards or whatever).
I can sell the same items for $3 in bitcoins and still make the same profit if I accept bitcoins directly.