I think the reason martial artists are cheapskates is because it is usually a long term endeavour. With skiing, it is seasonal (as with most sports) so the costs are only incurred for part of the time. Martial arts are a constant practice, so the costs are incurred all the time.
And, as someone has also said it is a bit of a niche market which to be honest is pretty saturated with suppliers.
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Behold, I see my father and mother.
I see all my dead relatives seated.
I see my master seated in Paradise and Paradise is beautiful and green; with him are men and boy servants.
He calls me. Take me to him.