Sounds wasteful but if we assume normalization of online ordering for clothing (where good fit is important) then this is probably the most efficient way to handle this situation. I suppose ordering a single item, trying, returning then ordering 2 more times until you get the right fit: that sounds a lot more wasteful than order 3 items in one go and doing a single return.

Now, IMO, ordering clothes (and shoes, or anything you're supposed to wear and where fit is important - at least important for a substantial demographic) through online shopping just doesn't seem to make as much sense as other things.

I personally rarely buy online unless I'm talking about staples like shirt and tees that I've tried from certain brands and know how it fits (so don't need returning).

As with other things... this huge shift to online ordering may make from efficiency perspective only when you ignore externalities and subsidies.