Sure the contracts are "long", but they both are only 24/25 years old and they both produce numbers comparable to what they make.
Trying to foist off Diop who pretty much gives NO production would be a non-starter.
Beans' injury history would make me hesitate, but looking at his #s when healthy he rebounds better than Okafor and has a comparable TS%. His eFG% has consistently been better than Okafor's as well. For 9 per I think the contract is irrelevant (again, assuming he can stay healthy).
In regards to Monta I don't think the value is there if the intent is to play him primarily as a PG (LB would kill him)...but if we could make him an offguard for a lot of his mpg teamed with a longer PG like Livingston I think he'd be well worth the money.