Your other option would be to throw your popular cards up on ebay and sell and use the money to buy the cards you want.
Some people like trading and don't want to spend any money, some people will do whatever they can to get the cards they want. That's personal preference.
I agree, I've never seen someone trade that many, unless they were really unpopular cards. Also, the info in the post you shared is 2 years old and with NH out now and the popularity, I think the market has changed. SP cards are pretty easy to come by and most people sell them for a pretty low...
https://www.animalcrossingportal.com/games/new-horizons/guides/villager-popularity-list.php
This may help you determine popularity.
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https://www.belltreeforums.com/threads/villager-popularity-guide-for-animal-crossing-new-horizons.482515/
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I think the best way would be to...
I usually check recently sold listings on ebay. I've found that there is a graphic floating around but it is flawed. If you check a few listings, you can usually get an average of what a card is worth.