Whenever you shop at Tom Nook's store, you earn points in Tom Nook's Point System. You gain a new status at different levels of points, and each status level gives you a discount on store purchases. You get more points for buying more expensive items.
| 100 bells = 1 Tom Nook Point |
After you spend 100 bells, you earn one more Tom Nook Point. Also, Tom Nook has special point days from time to time where you can earn more points per amount of bells spent.
Anything that you buy from Nook's store, including any items that you order from the catalog, will give you more Tom Nook Points.
A point special is an event at Nook's where he increases the number of Tom Nook Points per bell spent in his store. There will be an announcement about it on the bulletin board a few days before it happens. There is no way to predict when a point special happens. It is completely random.
The most expensive item that is available in the catalog is the White Katana. It is worth 36,800, so you will get 368 points when you buy one. There is also the Moon, which is 32,000.
The most expensive item that you can buy from Tom Nook's store is the throne. The throne costs 800,000. If you buy it from Tom Nook's store, you will get 8,000 points. This is a rare event, though, because it is a spotlight item. It is not available for purchase from the catalog.