It also really depends upon cost.

If they're simply building in an added cost over the average projected active device time (3-4 years average) and they charge $20-$25/year expectations might be lowered for what that service fee provides beyond online play.

Although If they want the average buyer to spend closer to $400 in addition to whatever games they buy over the lifetime use of the device it's hard to say whether that's to pad what is already a profitable device on Day 1 (still haven't read any BoM estimates) or simply to pay for whatever server rental and or maintenance costs are associated with the Nintendo Network, or whatever they're calling it.

I keep seeing posts saying Nintendo's online will be cheap. I think this will be the case but has any thing been confirmed?

Nothing. I refuse to pay for something that should be optional or completely free, even if it means I'm going to miss out on Splatoon 2 and other games that I could potentially play online. I'll just stick to the single-player focused games from now on :v

Splatoon

If I could play the games at 4k, I would pay over what Playstation or Xbox charge.

Likely I won't get it for myself, Splatoon is a mediocre shooter.

Pretty much my kid will ask me to get it to play Splatoon 2 online, so he's free to get it out of his allowance.

http://www.theverge.com/2017/2/1/14474430/nintendo-switch-online-service-price

In an interview with Japanese newspaper The Nikkei, Nintendo president Tatsumi Kimishima said that the service would cost between 2,000 yen and 3,000 yen per year, putting it in the $17–$26 range. Though details are light at the moment, the service will cover multiplayer gaming as well as offering users a free classic game download each month.

Splatoon 2

Nothing, at all.

Nothing. I don't pay on any platform and don't think I ever will.