The Trouble with Time (Time Rats Book 1) went on sale on 5th April 2016. Kindle Press advances are $1,500. In its first twenty-five days, TR1 earned $1,216.97 - but for some reason, UK royalties are not deducted from the advance, and TR1 earned £226.81 in the UK. So TR1 actually covered its advance, plus forty-something dollars, by the end of April. Sales and KU/KOLL reads of my other books have improved, too. My reader email list has grown.
TR1's current rankings aren't as good as they were for the first six weeks, but I know Amazon will be promoting my book later in the year, so I'm fairly relaxed about that. I'm getting on with writing Time Rats 2, which is the best thing I can do towards improving future sales.
My experience confirms for me that Kindle Scout is at the moment the biggest opportunity out there for most writers. It's not true you need a huge social media presence to be selected. You need a well-written book with a professional cover that Amazon thinks it can sell, and if you have a book like that, your chances of selection are high. As in the rest of life, luck plays a part.
I should add that not all Kindle Press books are doing well. Predicting what will appeal to readers is not a science. However, it seems likely to me that those books are still selling better than if they had been self-published.