see also: Rosin vs Solvent Extract Yields (not much there yet)
max theoretical yield is based on input potency. hitting the theoretical yield is far less likely with rosin than with solvent based extractions. Most report that yields are strain dependent. most doing in commercially are collecting trichomes first.
when you say “had a garden done” I assume you mean you had someone else make rosin for you…and you’re concerned that you got ripped off. do you know how it was made?