I'm not sure what “royalties” you could be thinking of. I doubt if his book is still selling all that much, and I don't recall seeing his TV specials being syndicated much at all – especially the older ones, though wouldn't that be nice? (Where, on the other hand, Blaine's specials were replayed several times in 2001). Copperfield's Got Milk ad does pop up every once in a while – but I can't recall the last time I saw it. There is the Illusions video – and I'd think that is direct sales going into his coffers (along with the other DC merchandise). There's no denying the Copperfield has twenty years on Blaine – and DB is just beginning to build his own “empire.” But I'd wager that the lion's share of DC's $60 Mil comes from touring. The guy is a workaholic, after all.
As for comparing DC's & DB's first Forbes appearances, I'm not a member of Forbes web site (and don't want to be), so unless someone is willing to do that kind of research (if the data is available there, and to what end anyway?), I doubt it will happen, considering – as you pointed out – that you'd have to calculate relative worth. We just have to come to the realization that DC makes more money than he'll ever need and DB is working on making more money than he'll ever need – but he's not there yet.
The last time I saw DC's double was a very long time ago, and it wasn't bad at all. I think many people tend to forget – because of the big illusions – that he was a fairly skilled manipulator early in his career, and he still does some fine close-up magic that requires sleight of hand skills. But you're right - his double is probably not as good as Matt's - and a lot of other people I can think of!
(Didn't make $5 or $60 Million in 2001)