And even if it was, the uptick in price is usually quite high; it seems most groceries have the highest margins on things marketed as healthy/sustainable.
Don't confuse margins with prices. I can't speak for the grocery stores, but at the producer level organic growing practices are higher cost. The farmer may get a higher price and yet also have a lower margin. That is certainly true for broad-field crops such as organic soy beans -- the higher price for organic at the grain terminal often does not make up for lower yields and higher input costs. I have seen broad-field crop farmers attempt organic and give it up as a risky, often money losing venture. (Source: I am a fly-over country landlord with skin in the game.)
Yeah, your point about the production costs is correct and seems easily generalizable. I don't think I can generalize the grocers the same way. This is an anecdote from 6 years ago, so take it that way, but in my area the average margin over all the stores and all of their items was just under 2%. Iirc, most grocers were taking losses on certain staples while maintaining a +50% markup on food marketable as healthy. I don't mean organic, just things perceived to be healthy. Some discount grocers and farmers' markets have opened business since then, so it may not be the same anymore.