Not really, since a “hexadecimal dollar” is really just a fictional measurement of money that Knuth has created (which he designates with symbol 0x$). I guess if it were $0x3.00, you could interpret the quantity to be regular dollars in hex form, which would just evaluate to 3, instead of the 7.68 Knuth is actually offering

The check is issued by the “Bank of San Serriffe” (https://en.m.wikipedia.org/wiki/San_Serriffe). Perhaps they have different typographical conventions...

That's apparently how Knuth writes it, so feel free to ask him. Maybe you'll get a reward too? ;-)

0x$ = 0x100¢ = 2.56$?