Harmonix has made an update to Rock Band Blitz today which adjusts the game's economy. Responding to players who have complained about the cost/benefit ratio of Coin expenses and awards in regards to using power-ups (which are a necessity for any high-level play), the developer has standardized the cost of power-ups across all songs as well as their rewards, which now pay out 100 Coins per star earned. This balancing of the economy will be executed server-side, meaning there is no actual patch necessary for players on any platform.
The changes should ensure that players who play well maintain their Coin bank while those who need more practice will be getting that opportunity when they have to earn back up a bit. The rewards for participating in a Score War have also been doubled, making them a more viable means of earning additional Coins.
These are good adjustments. Between accomplishing Rock Band World Goals, a decent collection of DLC tracks and my habit of practicing a song once or twice before trying to achieve Gold Stars, I haven't really struggled with my Coin bank. But if you're having a hard time getting enough, Harmonix seems to have your back on it.