Can't tell about the costs, but it's a misconception that chewing on sticks and stuff wears their teeth down. It's the chewing motion when eating gras, hay, weeds, leafs etc., then the incisors rub at each other and wear each other down. Pellets, solid vegetables, or even grains require different chewing, more ath the molars, too much of that in relation to the other stuff can cause problems with some rabbits.
Then there is the problem that mostly small breeds with cute faces have a higher risk of misaligned teeth, and that quite complicated process doesn't work right.
It's more likely your rabbits stopped gnawing stuff because of the teeth, not the other way round.
After reading here for some time I think it would be a good idea to ask for recommandations for an experienced vet in your area and put the financial aspect behind that criteria.