You might want to update this game since you can actually farm infinite money from the booster packs. This is because each pack contains 10 cards. This means at bare minimum each pack is going to be worth at least the buying price of $1,000 since each item card sells for $100. Of course each pack also contains 1 character card and will likely contain 1 or more equipment cards. The character card sell for $400 assuming you already have a copy of that card while the equipment cards sell for $200.

This can be especially abused before the tutorial since every pack you open will contain the same character card. So your guaranteed to be able to sell the contents of the pack for at least $1,300. Of course doing this during the tutorial bit will cause the screen to go entirely black after you've opened up a second pack, but you can restore the screen back to normal by simply walking into the store.

Regardless this trick makes the mini-games kind of pointless since you can just endlessly recycle packs until your opening 40+ packs in a row. Of course once you've gotten that far into the gacha hole your going to start wishing this game let you open up multiple packs at the same time.

So you either need to lower the resell value of cards, increase the cost of a pack, or ensure there isn't enough cards in a pack to reliably sell off the cards for money then you paid to get them.