The additional benefits on top of salary are substantial, and as has been noted they often have other jobs before, after and sometimes during their stay as an MP.
I don't think the remuneration is set at a level that would be a disincentive to those on average incomes considering standing for election.
I trained for my job for about 10 years. I train all the time to continue in it. I earn more than an average MP. I'm happy with the value I give in comparison; and I say that as somebody who does not believe all MPs are lazy, feckless and corrupt. Ours works very hard as seen from my dealings with him.
Bruce