Hey, thanks for the feedback, it's really cool to hear how deep you've gone on the game! We can't make any changes until the ratings period for the jam ends but after that I'll have a look at tuning the balance, it was a bit of guesswork for this version because we didn't have much time to test it.
The card removal and upgrades are intentionally too expensive to buy early as keeping your deck small makes thing much easier, I wanted to force players to bloat it up a bit before they started slimming it down. There is a bit of smoothing on which cards show up in the shop too but this could definitely be tweaked a bit more to be less swingy.