Not sure the price is about markup. The US has a slightly larger population, and a larger proportion of woodworkers owing to the space available.
It gets worse here in Italy, the price is double that of UK. I could not find the slot cutter for less than £60.
I do try to source locally where possible, and then from UK, with states as last resort, to support local trade, and reduce my carbon handprint....
I got my t-moulding from gremlin, and it was not so much more expensive, and sometimes, the delivery man bringing me a parcel from the US will charge me a 40% import duty, so it sort of evens out.