This is according to a recently updated FAQ page (via Destructoid) in which Nintendo mentions that users will be able to use My Nintendo Gold Coins to pay for subscriptions. However Nintendo notes that this cannot be used for auto-renewals, which suggests that you might need to keep purchasing it on a monthly/annual basis if you want to keep subscribed.
So how much will this cost? For those unfamiliar with how Nintendo converts gold coins, basically for those who make digital purchases, you’ll get 5% of the game’s price converted into points, where physical purchases are worth 1%. Each coin is also worth 1 cent, which means that for an annual subscription to the Nintendo Switch Online service which costs $20, you’ll need 2,000 gold coins.
This means that in order to obtain 2,000 gold coins and assuming you make all your purchases digitally (for the sake of simple math), you would need to have made $400 worth of game purchases to earn that many coins. This number will be smaller if you opt for month-to-month subscriptions at $8 per month. If you’d like to see how many points you have, head on over to My Nintendo to check.