Looks like the rockster is not worth it; the way upgrades for all kinds go up for it along with the measly payoff does not make the 10s spawn time worth it. You may want to balance that one a bit as well, I get way more by optimizing bally with 4 gunshot / 2 spikes / 3 lasers... Getting bally to 51.20K% and rockster to 400% are similarly priced, which basically means that I can get 5K+ from Bally several times per second, or get 28K from rockster after a minute or so...