You have to pay 19.99 euros to play online and trade Pokmon.
Pokmon Sword and Pokmon Shield will be the first games in the series to include an in-game purchase.
This type of shopping, usually associated with free-to-play mobile games, has become increasingly common in console games. In this particular case, there will even be an in-game purchase!
According to the official website of Pokmon, Pokmon Sword and Pokmon Shield will have an integrated purchase to join Nintendo Switch Online. This is Nintendo's online service that you must join if you want to play online against other trainers and trade Pokmon.
Nintendo Switch Online costs 19.99 euros a year and also gives you access to other perks, including a list of NES and SNES games, voice communication access (via smartphone app) and exclusive offers.