It depends on the budget and how good the band is. Anything under $10k monthly on budget won't get you any decent returns or followbase (a profitable one).
This budget would need to be spent on YouTube, Facebook, Twitter, Google Search and Network visitors. No you don't bot to the top like some idiots might think you can do, you simply bot to increase engagements and social authority aspects of your existing fanbase. You'd be wise to research into what record companies (the big boys) ctually do in order to drive up sales and fans entirely black hat with big money).