If it was about about Money, then you are looking at a number bigger than a "huge Cheque".
By all rights, Ditko deserves royalties for every toy Spider-Man sold, every appearance in any commercial or cereal box, every cartoon, and so on and so forth. Same as say authors of books gets, or George Lucas got for every Star Wars merch sold.
All Stan Lee came up with, as per Jack Kirby (the first artist who he approached and who invented the idea of the hero living with his Aunt and Uncle), was the name of the character and the idea that he be young. Everything else that defines Spider-Man comes from Steve Ditko. That includes the costume, the colors of the costume, the entire concept of powers, the web-shooters, and also Peter Parker's looks.Then you got the fundamental issue that Ross gets Stan to admit. Stan openly says it, he thought up Spider-Man. (From his perspective) He is willing to give Steve some credit but ultimately he was the one who thought Spider-Man up not Steve Ditko.
Whereas Steve from his perspective clearly doesn't think that's good enough.
This is a what if question but if Stan had had a different Artist than Steve would Spider-Man have been as big ?
Peter Parker in AF#15 is a dead ringer for Ditko in his high school yearbook, and Midtown High School was modeled on the high school in Pennsylvania that Ditko attended.
Ditko peter.jpg
If you consider the fact that most of Spider-Man's income is generated by merchandize and toys, i.e. people see Spider-Man in costume and know his powerset long before they find out he's Peter Parker or hear talk of "Great Power" and "Great Responsibility", then the fact is that Spider-Man's income is largely based on Ditko's design and not anything Stan Lee did.