Skiing does make for some examples of a couple weaknesses in the heuristic, though:
First the "best equipment you can afford" part is pretty poorly defined. Suitability of ski equipment is contingent on the skill of the skier and the type of skiing, so you can't just pick the most expensive thing and expect it to be the best for you. Skis are especially nasty in this regard in that the most expensive equipment often makes performance trade-offs that are actively hostile to beginners or use in the wrong conditions.
Additionally, ski equipment is consumable (at least in the hands of an aggressive skiier), which largely invalidates the cost-optimization rationale of the heuristic.
Skiing probably wants a somewhat modified heuristic, along the lines of "Start with the cheapest tool, use it until it wears our or you find an intolerable problem, and then choose a replacement that solves the problems with the previous iteration."
I feel like you're running into an issue a lot of rules of thumb have, where there are words that provide plenty enough wiggle room that the heuristic is accurate... but if you know enough to know how they should be wiggled then you don't need the heuristic.
If someone starts riding trails on the cheapest, or near cheapest option, they're going to at best have a bad enough time to be dissuaded from doing it, and at worst actually end up hurting/endangering themselves or others.
Not to say you need to run out and buy the most expensive bike one can, but there's certainly a balance to be had.
As an example, I was nearly completely discourage from learning the guitar by the first guitar I bought. It was a really cheap stratocaster clone (<100$) with a really bad amp.
The thing was so bad that playing it was uncomfortable, and it was not even able to stay tuned thanks to the crappy machine heads.
Looking back, I would have been better off buying a decent guitar from the get go, something in the range of 200$ would have ensure that (brands like Ibanez or Cort are able to produce quite decent guitars in this price range, even Squier (Fender low price brand) could be decent enough).
The point is to at least invest a little, usually avoiding the absolute lower price items, but targeting items one level above.
I had a homework problem in some math class about the optimal online algorithm for deciding when to rent vs. buy. It works out to "rent until you've spent as much as you would spend to buy, then buy," and I think that applies well here. You may spend up to double the cost, but you avoid spending _a lot more_ on incremental upgrades before getting gear that actually fits your needs.
It's like the tool already was the minimum viable level, then Walmart stepped in.
I won't buy anything with a motor in it from harbor freight either.
I've experienced this pretty directly with skis. If you get the cheapest boots and skis you can, you'll find it harder to learn, to the point where your feet hurt at the end of the day. I pretty much associated skiing with pain until I got decent equipment. There is a level above which it isn't worth spending as a beginner, but it's a level that looks high to people on the outside.
These days, I don't look for the cheapest tool I can find, I look for the cheapest tool people seriously use—which is often 5–10 times more expensive than the cheapest option. I've had enough experiences in the past sabotaging my own progression with awful tools that I know it's not worth it.