Firstly, bath sheets and bath towels has different usage.
Bath sheets used as sheet to cover bed or long chair or something like that, for people to lie upon.
Bath towels are towels for people to wrap body after bath time.
The Second obvious distinction between them is the size and weight. Bath sheets can reach 100cm~120cm width 200cm length, even further.
Bath towels usually 70cm ~ 90cm width, 130cm ~ 160cm length.
Since bath sheets generally heavier than bath towels so accordingly relatively more expensive.