[roadranger]

Variety and competition is always good...

I think if you can offer Tamiya parts consistently, and offer custom built trailers and trailer kits, along with aftermarket parts, you should do well.
Another untapped market is styrene truck cab kits, like Mack R models, Peterbilt 379's and cabovers, KW T-800 and cabovers, Brockways, Ford Louisvilles.

In defence of PMD, a lot of his stuff comes from Germany and is expensive to start with.
A lot of the locally made small run custom parts like air cleaners, battery box/steps, and Budd wheels are just as expensive...