I think you may be referring to an image from this What-If article, where the capacity of a gallon of MicroSD cards is estimated at 1.6PB per gallon:
When you're looking at the same price for two systems, and one is 100x-1000x faster at the cost of being 'merely' hundreds of TB per gallon instead of a few PB per gallon, nobody is going to bother engineering the latter just to save a few bucks on shipping.