Speculatively I suspect that trix pricing is such for sales reasons rather than cost grounds. Information online will definitely show that Trix has been much less of a success than Carpro would have liked. This is no criticism at all and the nature of business is such that every new product cannot be the success that Iron-X has been. As such I suspect that the pricing is based on the performance and popularity being lower than intended.
Initially Trix was claimed to have equal strength to tar-x and iron-x but practice has definitely shown otherwise. Now, in my view it does work, at least to a fashion. It will not work as well as the individual components. It also requires constant shaking otherwise the tar and iron removal ingredients will separate. If one fails to do this, you will end up spraying only one of the two components and, as the OP alludes to, this can mean almost total ineffectiveness against the other.
I have formulated comparable products and whilst the separating is avoidable, some of the other characteristics described do seem to be difficult to avoid. In particular I note the trim staining and browning of rubber tyres - I have seen this repeatedly with test formulations and have no really acceptable reason for this occurring (often the incorporated solvents in isolation do not do the same). My only advice is that you are very careful around trim.