For Twitch Prime members only, Amazon offers a Nintendo Switch Online 12-Month Membership for free. (Click "Claim Now" to initially get three months; once you've had an active Twitch Prime for 60 days, you can then claim another nine months.) That's a savings of $20 off the yearly price. Nintendo Switch Online includes online play, access to classic NES games, and other benefits. Some exclusions apply.
Note: After your 12 months, you'll automatically be billed for another year at the regular price unless you cancel the membership.