The "doubling" thing you mentioned is actually a bug. It didn't come up (that we noticed) during our own playtesting, so it will be fixed once the jam ends. That and we'll make the noise a little less grating.
The numbers of prices and values were all very... random, I'll be honest. There wasn't much thought into balancing it out, but that will most DEFINITELY be fixed.
I'm thinking about changing chum to increase how common rare fish are, not how often fish spawn period. Hopefully that fixes that issue.