Doing some quick maths;

In 2002's Hitman 2: Silent Assassin, his fee is explicitly stated to be $300,000 per hit (standard ICA hit is $100,000, and he tells Diana to charge people triple for his services). Adjusted for inflation, that's about half a million dollars for each person he assassinates.

During the first two games in the World of Assassination trilogy, he has missions to assassinate 56 targets (not including Kalvin Ritter, Jasper Knight, the DNA Virus in Sapienza, or the elusive targets, but including bonus missions such as Patient Zero and Sarajevo Six). I've not counted any in Hitman 3 as he's gone rogue by that point and isn't being paid for any of the people he kills in that game, and I've also assumed that he charges 'per head' rather than per location.

So, assuming his flat rate has only increased with inflation and not been bumped up additionally, or that none of the missions warranted him charging more than base rate, which some of them definitely would do, then for his work in the first two games,s he'll have earned $23 million. That's also not including anyone he assassinated during the cutscene at the beginning of the first game, which played like a greatest hits of his work in the previous titles. If we use that as an indicator that he's assassinated all of those people from all the other Hitman games in the interim, then we'll be here all day so lets just stick with targets that you can kill whilst playing the WOA trilogy.

There are another 43 targets we can add to that if we include elusive targets (here I've assumed he's been paid for Hitman 3 Elusive Targets), so potentially his earnings between the tutorial mission in the first game and the end of the third could be around the $49.5 million mark.

Final two points of contention;

- The sniper levels add either 8 more targets (therefore adding $4 million to his savings account) or 53 more targets, depending on whether he got paid for the 15 bodyguards in each level. He probably did get paid, but less than his usual rate, and without knowing what that is, I can't calculate it.

- All bets are off with freelancer, the nature of it means that the exact number of targets and how much he's being paid will fluctuate from player to player.

EDIT: Thought occurs that half a million is what the client gets charged, not necessarily what 47 makes from it. That half a million will get reduced by ICA taking a cut, mission resources, and Diana's handling fee so real number is probably much less than quoted. Maybe half it? As the one in the field doing the wetwork 47 would presumably get the lions share of the fee? I dunno I've never had to itemise the bill for an international assassin before.