> The original price was supposed to be $39,900. However there has been >20% inflation since then
That price was announced with a significant lead time, so at least 5-6% inflation was built in already.
> and the base model should be eligible for the full $7,500 tax credit applied as an instant rebate at purchase time, which was not available at the time of announcement.
It wasn't available that exact moment, but it existed.
> All that to say: the price actually paid will be $55,485, vs the inflation adjusted original base model price of $48,912 (possibly higher if there is more inflation before the release next year). So yes, the price you'd actually pay has gone up 13% in real terms over the announcement price.
I'd put the inflation-adjusted price at $46k, and not use the $7500 to reduce the difference, making $63k a 36% increase. Or I'd apply the $7500 to both and get 44%.