Yeah razor thin margins is barrier to entry that amazon sees as an opportunity not a threat.
Not exactly - Amazon has traditionally entered spaces with...not exactly razor thing margins, but margins with some wiggle room. Even their grocery play was on 'higher end' groceries and not a razor thin market like Acme/Shop Rite/Kroegers.
They then proceed to wrench out that wiggle room to drive out the established players and create an impossible barrier to entry.