I price my stamps at a percentage of catalogue value, considering condition etc, plus a little bit. For that reason, I accept offers and hold regular snap sales.
It's Australia Day on Monday (26th), so I'm having a 26%-off storewide sale.
Pricing needs to allow for this. Listing your items at the lowest price on the internet doesn't take into consideration human psychology. Buyers want sales, and specials, and want to make offers