And the production company and the Eggheads (or their agents) are not likely to tell anybody what they earn from the programme ! That will be a secret, not for public knowledge.
Being full time doesnt enter into it. You are either paid by the show or as a contract per series. It is very likely that the total renumeration exceeds the average wage even if they aren't working 40 hours a week.
I remember when Play Your Cards Right was on LWT, they filmed two episodes a day over a couple of weeks. Brucie certainly wasn't paid two weeks money though.