They usually are free to play with predatory monetization mechanics. That was especially back in 2016 when thanks to these games, the mobile gaming revenue outpaced PC and console gaming revenue.
Shoutout to Slay the Spire, Balatro, and Slice & Dice. They all cost a bit (around 10€) but are excellent ports of the originals and among the best mobile games. Slice & Dice even started out as a mobile game and was ported to PC later.
Plus mini metro, terraria, don’t starve, wild rift, and TFT (last two are free to play, and only have cosmetic transactions)