Hmmm, good question. For me I wouldnt hesitate buying online if you get a significantly better price. If you are commited to buying bikes from this LBS then you are already giving them quite a good deal of business. If you find something online that you want to upgrade a part of your bike with, give the LBS a chance to match the price or least try and be competitive. If they quote you a price that might be within a few dollars on any online price you can find then buy from the LBS and support a struggling industry.
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In his surreal surroundings among the clouds, this was his flight! Until, he saw the master caution light.