Market value is how much it can be/is sold for. Use value is the value it has not to be sold but to actually be used (which often has a direct economic expression, especially the use value of manufacturing equipment). You know what production cost is, the combination of wages paid along with materials, rent, etc. paid (in all cases, given value by other labor but filtered through market value) in order to produce something such as a commodity (item made to be sold).

So any single commodity has for itself at any given time: The cost of its production, the price you can sell it for (these two are different in part due to the monopolizing nature of their being only so many means of production), and what the commodity is actually good for besides selling it.

Most of the supposed counterexamples they mention in the thread have a non-zero cost of production (or very high, in the Juicero case), but virtually zero market value (because people don’t want to buy it) and disproportionately low use value (because it’s gadgetbahn or macaroni art or whatever).