Last time I bought tires, I think from Merlin, they came in a bundle of tires and tubes for a few bucks cheaper than other stores sell just the tires (GP4kIIs), so I basically got the tubes for free and then some. Bought a few more tubes that were on sale too for cheap, and probably have a lifetime supply now. This is probably one of the cheapest aspects of cycling, I wouldn't worry about a dollar or two here. Of course if you flat frequently maybe it's a bigger deal. In my couple years of cycling so far I have not had a single flat, knock on wood.