Cleanup Crew Misnomer ??

[fragNplug]

I have had a number of reef tanks for a very long and have always been setback at the so called experts and their recommendation of 1snail and 1crab per gallon of water.

I have one 45 gallon tank with 4 crabs and 3 snails, and everything seems inplace.
My other ones have more but i still have wondered if there was every a reasoning for this other then retailers trying to make a forutne.
Considering a hermit crab is 5$ and a 90 gallon tank would require 90 thats 450$ in crabs, say the same for snails your looking at 900$ for a basic cleanup crew.
Your ideas?