If you want to stay poor and struggle, be an owner of a bicycle, music or astronomy store just for a short list of brick and mortars that I've done. You get really good at chasing your tail to stay open.
That said, none of us should give our earnings away needlessly. It's already been said, buy locally when you need too. If that doesn't allow an LBS or whatever to survive, then it shouldn't exist. It's up to the retailer to pursue the future in a logical, sustainable manner. We don't help by purchasing things that are grossly overpriced. If the purchase doesn't make good sense then by all means don't do it.
Overhead costs are enormous compared to the potential return in most locations. It's been an exceedingly long readjustment period for property owners who are tied to financing costs for land, property, etc. "Everything escalates except my income" is a common cry for any land based operation or tenant. Again the retailer has to readjust the future operation to compete with the "new" and future realities. Personally, my stomach wasn't strong enough and although I ruined some very fun hobbies attempting to make businesses, I have recovered some of the former fun.....
I'm not going to bother ordering on-line if I am in a store and the differential is a small percentage larger. I will not pay more than that small percentage larger because it would not be fair to me (or my family) to do so. Markups should be what they should be for the item's cost/worth, not a handout to whoever is the provider.
Now, can I go ride my Ironman?