Agree on all counts there. The fact that the place merely exists does not count as "service." That's called overhead. If I go into the store and get no help, I see no problem with trying on to get a sense of size, at least so long as I neatly put the garments back on the rack.
I agree with Johnnynorman. I would have not compunction against using a discounter with non-existent customer service as a "trying on" station, but I think that going into a store with customer service, especially and independent store, you should go in in good faith. You can of course, inform the salesperson upfront that you don't really have the funds to buy at the retail prices. A good retailer is not going to bustle you out of the store. His key interest at that point maybe to develop a good relationship with you. At least, the reputation of the store will benefit (word of mouth is a great form of advertisement), and at most, you will end up seeing something unique and interesting that just can't be found on Ebay. Just trying getting a Baltazar or Engineered Garments, or even Paul Smith belt or John Varvatos or Jack Spade bag (and not those crappy ones that end up on Bluefly) on Ebay, and you'll see that they just won't be found there.