So then ask yourself, is warehouse capacity going to be constrained? Or will there be lots of warehouse space and lots of people who can create a web frontend to pair with that warehouse space?
Look, I love Amazon, I'm just telling you the 'low cost provider' wins thesis is one that people repeatedly get wrong because the low cost is often due to a technological advance that results in overcapacity in the industry.
Remember, even then, you are comparing Walmart to Amazon...not JoeSchmoe.com to Amazon. If you think it just amounts to putting things in a box and calling UPS for a pickup, I double dog dare you to compete with Amazon. It doesn't get any closer to a pennies-on-the-dollar comparison.