Good point, I've only started consuming bivalves recently (having never purchased them in my life before) and live on a marine coastal city where bivalves naturally wash up on shore in addition to being farmed, so I didn't consider that the prices I see would be significantly different than a non-coastal place, especially since I also often purchase mussels, clams, and oysters which are harvested in other countries and shipped here.

For me, I may spend the same amount on bivalves as I would on an equivalent (by protein content) amount of mock meat products or veggie burgers. The bivalves are no doubt much healthier, but have fewer calories which is either a good or bad thing depending on what you're trying to optimize for.