Its an irrelevant question. Bosh isn't under contract with the Raptors. They cant force him to sign with a certain team to look for a better deal. But since you asked the Mavs could offer up the fake Dampier contract, Rodrigue Beaubois plus picks.
Do Bosh and Lebron want to earn the max? If so they must do a sign and trade with their teams first or
leave 20-30mm on the table. Your trade off the $$$ doesn't match unless they threw in $$$.
This isn't true. Most of the difference in the contracts between what the Cavs can offer and what other teams can offer is wrapped up in the 6th year that only Cleveland can offer. The difference in money is about $5 million over the 5 year life of the contract. So it works out to an average of about $1 million a year. Certainly a lot of money but not all that significant relative to the ~$20 million average he will be making each year in the deal.I don't think Lebron is going to waste a lot of time worrying about that extra money. He may, as a good will gesture, let Gilbert know he is going to sign with a certain team and give him a short window to work out a sign and trade to get the Cavs a little something back in the deal and Lebron a slight bump in pay. The Cavs will likely decline because it will be a huge PR hit to do a sign & trade but if they do try they will have a couple of days to work with the team Lebron tells him he is going to. If they don't get it done quickly it wont happen.
LeBron holds all the cards here and isn't going to waste a bunch of effort on the logistics of a sign and trade.

Maybe breaking down Lebron's contract year by year with say the Heat vs Cavs would help....and maybe a link. I didn't think years 1 thru 5 were any different no matter where he signs.
The exact number are not know yet for what a max contract for LeBron could be. The 2010-11 Salary Cap figure will be set by the league on July 7. Right now the cap is projected at about $56 million. There are only 2 options for Max contracts - what the Cavs can offer and what any other team with available cap space can offer (Heat, Knicks, Bulls, Nets, Clips).According to the current CBA:
The most a 7-9 year vet can make is 30% of the cap in the first year of their contract.
Link
The Cavs can offer 10.5% annual raises. Any other team can offer 8% annual raises.
Link
The Cavs can offer a 6 year deal other teams a 5 year deal.
Link
So assuming a $56 million cap next year the first year of Lebron's contract with any team next year will be $16.8 Million. From there Cavs vs Other:
Year 2: $18.564 vs $18.144
Year 3: $20.513 vs $19.596
Year 4: $22.667 vs $21.163
Year 5: $25.047 vs $22.856
Year 6: $27.051 vs New Contract
So the Cavs can give him $130.642 over 6 years and any other team can give him $98.559 over 5 years.
In the first 5 years of the deal the Cavs can offer him $5.033 more than any team.
The 6th year is a huge unknown because the current CBA ends after this year. It is possible the Lebron could get more than the $27Mil in this deal from a team in free agency under the new deal. It is possible he could get seriously hurt and not get a new deal. I is possible he can get a bigger deal in 5 years from now compared to 6 years. What if he takes the 6 year deal and gets seriously injured in year 6. He wont get a max contract and ends up out a lot of money he would have if he got a new deal in year 5.
LeBron and his team understand there are risks going both ways with the 6th year in a deal. How they evaluate that is a complete unknown to anyone but the people in that inner circle. There are valid arguments both ways. From an outside perspective we have to assume it is a draw and start to look at the other factors in the decision. The $5 million more over the first 5 years, the chance to win a championship, being in a city he is comfortable in, being in a city that maximizes his marketing value. These are all factors that are going to weigh more heavily than the 6th year of the contract. Remember that last time Lebron negotiated a shorter contract than the max with Cleveland.