You are right, you did address our situation (and I largely adopted it when I said I'd do a deal subbing in Garcia for Udrih in a heartbeat despite the longterm financial implications).
As for the other teams, they just don't owe as much money in future years as we do, and they don't have to resign a key starter coming off a rookie contract next year to tack onto it. With an extension for Rondo at a reasonable $10 mil a year salary, we'd already be at $55 million for 2010-11 (for Perk, Rondo, Pierce, KG)
Cleveland, on the other hand, will only be at about $38 million WITH Lebron resigned to a longterm deal (factoring in a $2 million raise beyond what he could get on his player option for that year) and can chop off $4 million more by trading or not keeping West (whose contract per Roy is not guaranteed for that year and who would become superfluous with Mo, Martin, Udrih, Gibson and maybe Garcia in the backcourt). Houston will only be at $28 million with Yao's option. Chicago will only be at $35 million after exercising team options on Rose and Noah (and Rose doesn't have to be signed to an extension until after 2012). Miami will only be at $29 million with Wade signed to a longterm extension (again factoring in a $2 mil raise) and after exercising team options on Beasley and James Jones. Those teams just have much more room - $17 to $27 million more - to take on the contracts.
I apologize, I thought I had included all that future salary information in previous posts but it appears as though that part may have been eaten by the machinery of CelticsBlog (serves me right for writing such long-winded posts).