Self pubbing erotic shorts

I'm giving a whirl at self pubbing a series of erotic shorts, between 5K and 6K words. The theme is cyborgs. I anticipated pretty much no sales, but I figured self pubbing them would be better than having them take up space on my hard drive, and no pubs I know take stories that short.

I released the first one last Friday and the second today. Both are priced at 99c at Amazon and All Romance Ebooks.

After one week:
Sales at All Romance Ebooks: 3
Sales at Amazon: 10
Refunds at Amazon: 1

12 sales total. Better than what I expected after a week, for sure. We'll see if they stagnate or not, though. For money reasons I'm using the same basic cover design for every book in the series, and I'm hoping readers don't get confused.

Not the most exciting journey yet, but it's something.

Something weird:

Since release early Saturday morning, the second book, Only Human, has sold 7 copies at Amazon. Apparently that's all one needs to hit top 100 in:

• #81 in Books > Gay & Lesbian > Literature & Fiction > Erotica
  

There's either an error somewhere or there aren't as many well selling erotica shorts as I thought.

I plan to release the third book in the series this Friday. For now, my sales are:

All Romance: 13 total (7 of book 1, 6 of book 2)
Amazon.com: 21 total (12 of book 1, 9 of book 2, with two refunds)
Amazon.uk: 5 total (4 of book 1, 1 of book 2 )
Amazon.de: 5 total (2 of book 1, 3 of book 2 )

42 copies sold total in a bit less than two weeks. I have no basis for comparison, so I don't know if this is good or bad, although Only Human hit #58 out of 100 on Sunday before dropping. For .99c stories, though, royalties are meh. I'm hoping this will translate into good sales for the eventual anthology, though.

Quick update before the next book goes up (once I stop derping up All Romance)--76 copies sold in the past three weeks, assuming I'm doing math right.

Yeah, I'm surprised. My biggest seller by far is Only Human, and I'm not sure why that one took off so much. Maybe the title? The length (its the shortest)? The somewhat red background? The content (mild BDSM)?

I've got one more story planned and then the anthology. For a little experiment, it was pretty successful.