I assume they're paid based on the viewership the shows they're on attract... So it makes sense when, say, it's someone like Graham Norton who love him or loathe him very much "is his show". Linekar though...
... his viewership is high because football is popular. And that's pretty much it. They could put a hat and glasses on a honey glazed ham and prop it up with a voiceover chatting about footy and the viewership wouldn't change.
So I guess the question isn't "why are women paid less", so much as "why is it usually men who are picked to front the biggest shows".
The Chris Evans conundrum I have said before I will just never understand. WHY does anyone want to see him or hear him at all. Ever.
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[edit]Also just having briefly looked into it, Norton is actually potentially the top earner, as he's only paid directly by the BBC for his radio stuff and Eurovision and things like that (the figure of £600,000 quoted in the article). With the show, the BBC pays the production company that makes it who then pay Norton. His total income in 2017 was well over £2 million. So basically a lot of the direct figures from the BBC are meaningless...