i don't think you should bother, maybe he don't have that much money to spend or he wanted to test the game before buying,
i played rimworld on a friend's house, and i liked the game, i went home and looked at the price, here on Brazil the game costs R$ 56, which is pretty expensive for a indie game, it's almost a triple A game, even that i've managed to buy it with discount it was still expensive, so i think you shouldn't care that much for someone that got the game for free, not everyone can buy things.
i played rimworld on a friend's house, and i liked the game, i went home and looked at the price, here on Brazil the game costs R$ 56, which is pretty expensive for a indie game, it's almost a triple A game, even that i've managed to buy it with discount it was still expensive, so i think you shouldn't care that much for someone that got the game for free, not everyone can buy things.