An awful lot of people advocate for mixing your own rub, on the basis of cost. There is a cost to mixing your own rubs as well, and it can add up in other ways. It takes time to get the ingredients, mix the ingredients, all the measuring as well. Depending on your operation, the loss of opportunity while mixing rubs might be enough to argue for buying a commercial rub that you prefer in bulk.
The same goes for sauce, using a commercial sauce base, such as Cattleman's and tweaking it can save you a lot of time. Time always equates to money.