Some years ago (2006) I did a cost comparison of PPG's "economy grade" OMNI MTK single stage urethane and PPG's "premium grade" Concept DCC single stage urethane. The mix ratios of the two products are different as are the costs and the costs of all additives. I did the comparison on an RTS (ready-to-spray) basis. One quart of MTK RTS was $19.82 and one quart of DCC RTS was $59.93. I assumed that any leftover reducer was not wasted and could be utilized at other times. That makes DCC about three times as expensive as MTK. My past experience using both MTK and DCC is that DCC is quite obviously a higher solids product and covers better than the MTK. While I use three coats of MTK, I only need two coats with DCC. Incorporating the coverage difference into the RTS cost difference, concludes that topcoating any object that requires one quart of RTS material per coat will cost $120 using DCC and $60 using MTK. By that analysis, the DCC costs twice as much to cover the same object as the MTK.
My personal opinion is that for the DIY that only paints on an occasional basis and does not count his time as money, then the DCC is not worth twice the cost, although one could weigh the value of the extra risk of screwing something up during an additional coat. On the other hand, for someone whose time is money and making a profit is the incentive, then the premium DCC might well be worth the extra cost. Plus if one is experienced enough to be able to get adequate coverage in a single coat of DCC, then the cost is awash and the decision is an easy one to go with the premium product.
I think that even B would agree that the PPG's "economy" epoxy primer (OMNI MP-170) is just as good at a far less cost than PPG's "premium" epoxy primer (DPLF). I used to use the premium DP (before they took the lead out and called it DPLF) and always found it to be an outstanding product. Quite some time ago however, I moved to MP-170 because of cost. After using that for a number of years, I see no reason at all to go back to DLPF, at least for a DIY doing his own work where there are no warranty issues to consider.