Saving a few bucks today could cost you dearly down the track. When it's no longer viable for bike shops to stock tyres and fit them for free you might find your bike off the road waiting for your internet purchase to arrive and then having to make a booking to have it fitted at a price that eats up most if not all of your saving. You should seriously think about supporting the businesses that provide the convenience of ride in/ride out, on the spot fitting or be prepared for a loss of convenience and amenity and evaporated savings. Just sayin'.