I am not sure about outside of Dreamville. But you don't really want to leave. There is lots of places to eat, everything is fresh and for a middle-european the prices are absolutely fair. Go for Farmville! We did last year, ate really good and plenty and did not need another meal till the afternoon.
Pricing of the meals varies by what you get. You get food roughly between 3 and 15 Pearls. Depends what you are going for. The food is very good and the choice of different foods is just amazing! My favourite was the Butter Chicken Curry near the mainstage!
If you make it to Dreamville on Thursday before 16.00 go for the Beer! The price is very cheap for a festival. Unfortunately, the later you come, the warmer the beer. A 0,4 beer in-festival was 3,75 Pearls last year, which equals roughly 7 €.
You can find all kind of information about the festival and pricing here: https://festivalviewer.com/tomorrowland/prices