A really solid game! I think the bartering system is super cool, but given that there is no downside to it I could pretty consistently grab 3-5 heals for 1-5 gold and pretty easily reach over 100hp. I think either ramping difficulty in the waves or adding a downside to bartering could help counteract this. Regardless, a fun concept with the 10 second windows, and an enjoyable time.
I'd really appreciate a rate of my game. It was my first jam, so all feedback both good and bad is awesome: https://itch.io/jam/mini-jam-130-lunar/rate/2020903