Avg player doesn't buy a few thousand cards at a time. If you buy a high value card from a random seller you should always check it unless you trust them from references.
People only pull out slower tools for valuable, forgery worthy cards.
If someone is buying 1000 $1000 dollar cards, it’s still worth it lol.
Even cheap forgeries cost money to produce, so I wouldn’t expect a lot of low value cards to be forged. If you sort out the valuable cards and do random sampling, you can probably catch the most problematic cases.
For Mtg cards, the green dot test is very easy to learn, and I’m not familiar with any fakes that pass it.
(Edit: arguably you have to worry about rebacking with the green dot test, but rebacking is typically pretty fishy looking.)