I sorta figured him to be worth something like at least million on paper, with his house, "income" from Barone Sanitation and his various assets.
In reality though, i pictured Tony as being worth 2, 3 or up to 5 million (on the outside) on the street; that is, all his money on the street, the sum of his rackets and points in various business, the "kick-up" from his "Family" (or as Big Carmine put it, "glorified crew") and , of course, the money he has stashed in his off-shore accounts and varoius nest-eggs.
Nothing to sneeze at, and far beyond his father's and uncle's achievements, but still not exactly in the world of high finance, something i believe he's aware of.
I may be completely wrong in my assumptions, though. I live in Australia, where a million is worth a bit more. Heh.