There are entire books on this subject.
MOC is a big deal, pay more up front for material with longer life and less maintenance, or build cheaper and just replace/repair what needs it as it fails. If you count the cost of lost production the first is almost always less expensive in the long run. But it takes more money up front, and since many plants are unsure of where the process will be in 10 years (feed stock, products, production volume)there is a good argument to build cheap.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube