Sadly, our guess is usually as good as theirs. So we're indebted to Celebrity Management, which has been recruiting big names for ad campaigns for the past two decades, for spilling the beans.
At the moment, the big winner is Phil Tufnell who, according to CM, will be stuffing £25,000 into the pockets of his whites after bowling out the other contestants in I'm a Celebrity ... Get me Out of Here. His appearance fee before the show was just £1,500. Howzat!
The big loser? Angus Deayton, of course - CM reckons he'd struggle to get a bit part in a Pizza Hut ad. But no such worries for Samuel L Jackson, who trousered £1.3 million for Bartle Bogle Hegarty's campaign for Barclays.
The biggest chancer? Step forward Ainsley Harriott, who has such faith in his talent that he has agreed to link his fees for fronting Grey Worldwide London's Fairy Liquid spots to the number of bottles shifted. You've got to admit, he has chutzpah, if nothing else.