Cleveland could have given Boozer the money Utah gave him. If they did he would still be a Cav and the Cavs might have a championship.
That's not really true. Yes, as a restricted free agent, the Cavs had the right to "match". However, since Boozer was coming off his second season, they didn't have Bird rights. That meant the team would have had to clear sufficient salary cap space to be able to match Utah's offer, and couldn't do so.
After the same thing happened with Gilbert Arenas, the CBA was modified. Now, a team can't sign a restricted free agent with one or two years in the league to an offer sheet worth more than the MLE in its first year. If that had been the rule at the time, Golden State could have matched Arenas and Cleveland could have matched Boozer.