I didn't say they should leave the EU but they also can't really win in a fight against the purchasing power of wealthier countries in a single market when they can't import out of it other than via the existing EU channels.

Denmark imports tomatoes from Italy at the same duty rates as Bulgaria which are zero. Denmark has more money, normally countries would enforce both import and export duties since there are no duties effectively Bulgaria and Denmark and Bulgaria can only compete on price per unit and neither country can use any other tool to control the price.

If Bulgaria wants to import Tomatoes from say Turkey or Israel they also have to go through the EU red tape and effectively pay a "fixed" price which is more or less set to protect EU tomatoes growers.

Bulgria also cannot subsidize Tomatoes for the most part without violating EU regulations.

Now Bulgria gains a lot form being an EU nation, having lesser tomatoes is the price they pay.