Neopets has gotten much quiter than it was, but the current team is showing effort to fix broken parts of the site. Progress is happening slowly though.
Abrosia is still very good. The decline of users is also affecting the Neocodex database though. Most prices are still correct however. It seems that many people also use Valorsuite to autobuy. That one is also very good.
As for your strategy of selling few items for a lot of profit I don't think it will really work. Morphing Potions have deflated a lot and are hard to sell. Stamps have gone up in price because of newly released avatars, but personally I don't have much luck in the stamp shop. Many r99 have great price fluctuations. There are legit restockers on the boards complaining all the time because it's much harder to make a profit.
Recently there was a huge inflation of spooky foods because of a newly released avatar that involves Brain Tree quests, but that's practically over.