Have you checked the price of Stainless in the US lately? The price of steel, and stainless has about tripled in the past couple years. Rusting isn't the issue, stainless is awesome, I use it all the time, I love it.
Fiberglass on the other hand is much easier to work with, and once a mold is made, you can pop Bins off left and right, but I couldn't make them for no where near $125 delivered as Mike T stated, but definatley less than retail on a set of Momo bins.