I totally understand that, but compared to other commercial vendors, Xfrog price is not bad at all. By the way - on turbosquid you always buy a species, this means 3 models in each pack (should be nine in the latest ones, but I am not sure baout that), so the per model price on Turbosquid also is below 10,-.
I also think it would be nice if it would be possible for customers to create own, small bundles - but I think the only way to get something like that is to ask them directly.