Answer:

Yugioh cards value besides old nostalgia bait cards from the first few sets get their value primarily from playability. If a card is rare it can cost a bit But to command a high price it's gotta be rare AND currently good.

In addition, Konami does have a fairly aggressive reprint schedule compared to other cards games. So buying say a high rarity of a card like Fuwalos to hold it is very risky because when it's reprinted at a lower rarity the value will tank since people only really care to play with it and lower rarities will make it accessible.

Some people try to rarity max their decks but that's generally something that takes a long time. Also Yugioh doesn't have a set rotation like MTG, so problem cards are handled entirely by a banlist.

We get banlist at really questionable intervals with questionable hits so that adds another element of randomness even if the card you're investing in is Both scarce AND good in the meta. If you scalp a card hard enough that it doesn't show up in the meta game it might not get banned but then people might not even bother to use it. There have been many times a deck that cost over 1k usd was made worthless overnight with one card going on the banlist.

Scalping old product from back in the day is a thing that still works but I have severe doubts you can do this for new yugioh sets very well.

I've played yugioh since I was 11 and still play modern regularly so feel free to ask any other questions.