I will pay full retail anytime I am getting what I perceive as an element of service in the purchase. For example, I feel it is very inappropriate to go into a retail shop to examine alternatives, determine what you like, don't buy, and then go home and purchase on the internet. You're not doing right by the merchant for the service the merchant provided in letting you examine and evaluate your potential purchase. You received value but you paid nothing to the retailer who delivered the value.
Like many others have stated, I enjoy having local retailers that allow me to better evaluate my purchases before I buy and I am happy to pay for that privilege. Maintaining a retail storefront is an expensive undertaking and I have no regrets in paying my share to have access to this resource. In Austin, TX there are even bumper stickers supporting the eclectic shops in and around the city. The bumper stickers say "Keep Austin Weird" and it's a "Buy Local" message.