They knew that amount was close to the amount they had left to spend.
Here it is again, the notion that they really only had five million left in some 2012 piggy bank.
But you're making the exact same assertion in the opposite direction! Do you know they have more than $5M left in the piggy bank? Do you know what the costs to the team and ownership would be financially if they spend more than $5M more? Why are you criticizing others for admitting they are speculating, but speculating yourself?
I'm not sure what you want from me? I speculate that the team has a budget of $110M this year to spend on players. They've chosen to not exceed that budget for Oswalt. If McClellan were gone, it'd be possible to sign Oswalt without exceeding that budget. You're speculating they have more. So what's your point?
Actually I think there might be one way to tell.
If they trade McClellan and sign Oswalt?
No, that would prove nothing. If, as I noted above, they add eight million in payroll during the year--or, if in your scenario above, they dump KMac, sign Oswalt, but then during the year add an additional $2.5M in payroll obligation, equaling the KMac money they dumped--it would prove that the Cardinals did in fact have the money to sign Oswalt regardless of KMac but just refused to do so.