Australia has a number of large veggie producers that use glasshouses for growing and have been around and successful for many years. Look up Flavorite and Perfection Fresh for two examples.

A lot of the bell peppers and tomatoes for sale in Germany, especially in the winter, are grown in greenhouses in the Netherlands. They’re only somewhat more expensive than the ones grown outside in Spain at the peak of their harvests.

But wheat and potatoes? No, those are strictly outdoor things.

already mentioned, but the netherlands (pop 18m) is the second largest agricultural exporter in the world (after the US) — Driven largely by high-tech greenhouse operations.

Maybe not on a per-acre basis, but when you consider the acreage needed for commercial farming, it's untenable for the "family farmer." As a real estate agent, can I find you a generic alfalfa field that might kick off some vacation money? Sure - $11,000-15,000 an acre. Why is wine $500 / bottle? Because that farm ground is $70,000 / acre in some cases. You want to produce wheat, potatoes, canola, legumes? Now you are talking somewhere between hundred and tens-of-thousands of acres to actually be a player and make any money, so even at $15,000 / acre you are talking millions of dollars just to get in the game before you buy that $500K+ harvester, etc.