Even 80-85% sounds like too much.

Compare the legs of a slim person with the legs of a severely overweight person. It's like adding shake weights onto the legs that do the pedalling.

And overweight people have different weight distributions, some have the weight on the legs some in the belly. Depending on where the weight is, that's a massive difference.

Watts input and watts output is massively different with every machine (compare e.g. an electric engine with 90+% efficiency to a combustion engine with maybe 20-30% efficiency), and humans are no different.