Cheapest weekend would be to fly into Austin, Uber or rent a car, get a cheap hotel in bastrop and a gen admission or bleacher pass for the weekend ($99). You might be able to find a decent priced hotel in downtown or east side of Austin, to still be near nightlife and the track.
Bastrop is a decent size town just east of the track. You’ll always be in the opposite direction of traffic going to and from the track. No real night life there, but plenty of places to eat and such. Everything there is “normal” prices.
If you are into the nightlife I would stay in downtown Austin. Some of the dealers like Ducati Austin, will have bike shows and meets on that weekend. 6th street is all live music/party/nightlife stuff. Prices will ne higher though. Other than downtown, I wouldn’t stay west of I35, due to traffic and getting to the track.
If you drive down in a rv or do tent camp, you can tent camp in lot N where we will be. That’s $250 for the weekend though. Plus admission tickets.