Interestingly, I interviewed Steve Bell of Jagged Globe a couple of years back for an article on climbing Everest. I asked him what experience he'd ask for in a potential client for that expedition and he reckoned:
1. technical experience of Scottish grade 2 winter routes, but preferably harder as the harder you climb, the faster you'll move on what technical ground there is on Everest.
2. Past experience and successful acclimatisation at above 6000 metres. He reckoned 5000 metres is the point where people who simply don't acclimatise, hit a sort of wall. If you can acclimatise successfully at 6000, you can go higher given the right time and programme.
Note, those were his basic requirments, but what he actually preferred was a graduated progress through smaller 'big mountains' up to the 8000 metre mark. The programme said that the two guys had climbed Aconcagua as preparation, but Aconcagua is basically a high altitude fell walk and no technical preparation at all. Personally I wouldn't want to be on a grade 3 Scottish winter route with someone who apparently had so little winter experience, let alone guiding them on Everest. You have to ask whether he should have been there at all, but then if you're running a business and someone offers you $40K to take them up Everest, how easy is it to say no, go away and climb some other peaks then come back to me?