No, no, no, I don't mean give an illustrative example of how one might do the calculation. I understand how one might.

I mean that in actual practice, in the actual real world, untangling everything enough to come up with a good estimate is difficult. It's not too hard to come up with an estimate of the direct cost of labor for one particular product (at least if you run the textile manufacturing company), but when you have to push this calculation down through all the inputs into the product, it gets very involved indeed. When you then have to do this same calculation for all products that are comparable too, it gets harder yet.

And we haven't even talked about the wrinkle that linen itself goes for all sorts of different prices: https://www.joann.com/fabric/apparel-fabric/woven-fabric/linen-linen-look-fabric/

And this is all to calculate something of dubious value economically, even if it might have some claim to be of greater interest morally than the actual price.

And after all of that, it still doesn't explain some of the most obvious issues, like why the price of oranges goes up after a frost damages the crop. You aren't getting any more oranges. So the price goes up until few enough people think an orange is worth that much so that demand matches supply. No labor changed at all, and no labor can fix the shortage. You just have a standard supply shock, which marginal utility handles just fine, and labor theory doesn't.

I do think it's interesting to attempt to calculate the aggregate human effort expended on different things and note any major disparities between effort and price. I just don't think in a modern world with incredibly complex interconnections, and lots of short-term fluctuations in many industries, that it provides very much insight economically. Mostly it seems one would want to use it in a tentative advisory role (given the difficulty in calculating it) to try to motivate incentives and policies for getting people to expend effort in a more pro-social or pro-environment way.