I can list furniture items that sell for lots of bells, like Royal Crown, but since you'd have to obtain them before selling, it wouldn't be ideal.
If your goal is to make money selling, the best thing to do would be participate in the Stalk Market. Find players who have Daisy Mae with a low turnip price. Buy as much as you can. Now find players who have a high selling price at their Nook's Cranny.
On your own, just go fishing or deep sea diving. You can make large amounts of bells per hour doing this.
Check which items are the high selling items for the day...then craft a bunch of them. I've had plenty of times when the items being offered high prices at Nook's were simple items to craft, thus very easy to craft a ton of them and flip them quickly. The stalk market is a viable option...but, it also requires a full week to come to fruition (if you aren't time traveling or visiting others)...also, you aren't guaranteed to make more than you paid anyway. If Daisy is selling high, you probably aren't going to find any other players who can make it worth a trip anyway...thus, it's rather pointless to take the stalk option unless the price is already very low. All of those considerations make it kind of hit or miss.
But, yeah...if you have a ton of crafting materials like iron, clay, and the three types of wood saved up, it is quite easy to make a whole bunch of items and sell them on days when Nook is paying high dollar.
I have sold things at high sell prices like my non-native fruits and that kind of stuff. I know some of the things like pumpkins sell for high amounts and I collect seashells daily along with my new recipe. I have planted money trees to get money every day. I also purchase event items to sell later.
There's an exploit for when one of the high-selling items is a donation box, where you can sell the donation box after maxing it out and receive an inordinate amount of bells in return. This is a rather time consuming process, though.
There's an exploit for when one of the high-selling items is a donation box, where you can sell the donation box after maxing it out and receive an inordinate amount of bells in return. This is a rather time consuming process, though.