Are you under the assumption they are spending this money on turning it into a dirt track? If so, that's not the case. They are going to run a dirt race after they tear up the asphalt that is already there and then lay new asphalt down for next year's racing. I believe this is a one-and-done situation.
The idea behind the money is to generate mo' money with tourism/taxation. The novelty of a reborn NW, even if only for a few short years, will probably pay for itself in that time.