The salary cap is 32 houses worth the same amount that goes up in value 10% every year (that might be conservative with the new TV and streaming deals and the gambling rights for the next 10 years). Each team is given a home equity line on that house that you don’t have to pay interest on and a yearly salary cap for accounting purposes to preserve parity. If you wanna spend more this year, but push the accounting salary cap charge for it to future years, that’s your prerogative.
Credit card isn’t a good example because interest always accrues and you’re spending money you may or may not have. The salary cap is spending money you will have in future years today that doesn’t accrue interest and the money you will have in the future years grows 10% every year for the next 10 years. (Those media rights deals are locked in). It’s a debit card, not a credit card.