I think saying they can't live on £60k is ridiculous, of course they could if they had to or wanted to.
But, the kind of skills that make someone a good MP and being able to build the profile that gets them elected in the first place would mean they could easily earn more elsewhere.
It depends what sort of quality you want from your MPs, I suppose.
In theory, I would support legislation meaning MPs were unable to have other business interests because of the conflict of interest. However, how could you ever make that work in practise? Are they not to be allowed investments of any sort?
I do think that if they have so much time on their hands they can manage all these other interests, perhaps we need fewer of them!