Specialty fasteners are more expensive than regular ones. It's true in all industries... my exhaust flanges on my car use an m10x1.25 bolt and they were a 2 or 3$ each for a plain bolt in that thread size from the local fastener place. The actual shoulder bolts from the dealer were like 15$ and came with new springs... but it's only a few cents worth of steel.... kinda how it goes.

If the price of a track nut is too much to swallow just get flange nuts, they'll work almost as well and are much cheaper from aliexpress.