Sorry for the link to the news article, no idea how to link to the eshop.
A pretty good price for Splatoon, and the free 7 day online trial is pretty good in itself!
Go looking for this on the eShop on your switch and you should find all you need.
I haven't tried it myself if someone can confirm, but it seems you might have to try the demo first to get this price + the free trial?
@TheDukeOfNukem makes a point worth noting. There's not a lot to do in Splatoon 2 without Nintendo Switch Online. So if you do grab it, once the 7 day free trial runs out you'll have to work out whether you're willing to buy an online membership for 1 or 12 months as well.
@RocketSwitch also notes: "It has a full single player campaign mode, and has an 80 level single player DLC pack with brilliant level design."
Nintendo Switch Online is…
$5.95 per month
$11.95 per 3 months
$29.95 per 12 months
There's also a family account option for $59.95 per 12 months. This gives online to up to 8 accounts. They can be across as many consoles as you want, and works out very cheap with 8 people on board. Just beware, if you enter one of these memberships there will be someone who gets to decide if you stay in the family account or not. That is, they can kick you out early if they want.
Splatoon is pretty useless without the online though, so bare in mind that buying this after the trial, is basically just a way to try to get you to buy the online full time.