I am indeed referring to EREC data (click "sales" on the left menu, there will be more data there soon I am doing an update this week). Piers anthony also has a little data in this area if you search through his "publish on the web" site looking for "$".
That said, erotic romance the top selling fiction genre for ebooks and those figures are not huge. So if you want to make more that that, you may want to take another look at the larger commercial presses. They may be harder to break into but the investment can really pay off.
There are always exceptions but in my data set now of over 200 recent ebooks in the same genre, publisher is overwhelming the most important factor. There is surprisingly little variation in that Ellora's Cave book selling very poorly, relative speaking, still exceed even the top sellers of most of the other publishers books. With some presses on my list even their confirmed best sellers do not exceed 50 copies in the first year, and single figure sales are not unknown.
Yes, other factors have influence, but these are additive to choice of publisher--not something that makes them all roughly equal. The reason being that romance ebook buyers from top sellign presses buy directly from that presses website. You either have that readership, or you don't. That is why Ellora's Cave can remain clearly the top seller despite while not currently selling any appreciable amount of print and not using any online distributers other than their own website. (And I expect Samhain to be challenging their position soon, but that is just my 2c prediction).