This question has been answered many times in the last year and we now know some important things about full or part-time independent as well as hobbyist iOS game developers:
Here's why: the median earnings are almost linearly dependent on the amount of games you've published previously. If this is your first game, it'll most likely bring in just 500 bucks. I really recommend you check out the numbers of this survey for yourself, so that they seep down into your expectations of what you can realistically make out of this business.
Thinking you're somehow going to outrun this is like planning to make a living by playing the lottery. Sure, it happens to someone, but it'll not be you.
There's something more I can add to the above numbers, and it's the story of not giving up. It all starts with the game's initial appearance on the App Store, when no more than your friends and random strangers shuffling through new releases buy your app.
You're happy that your first game even made it through the App Store review process, and you spend the night drinking with your colleagues, collecting bets on how many sales you'll get on the first day. We got 52. We released on Thursday and the number stopped at 260 at the end of the first weekend.
Monkey Labour weekly sales (version 1.0)
The project lead sent about 30 emails to various websites, trying to get the game noticed. We got a couple of good reviews, and even a feature from Apple under new and noteworthy games. That's usually a big deal and can greatly drive your sales, but not in January 2011. That's when Apple took away the usual games link in the App Store in exchange for a Best of 2010 retrospective. So for the whole time we were supposed to be featured, there was no way to reach that list on an iPhone. Needless to say, those few that saw it through iTunes didn't help our release much. The sales reached 270 in the second week, and then halved with each following one.
By the end of first month we already reached the miserably low long tail with about 10 apps sold per week. Total first month sales: 790. With about two thirds of the $1.99 price coming into our pockets, you can imagine we weren't jumping up and down in excitement. It was before the above-mentioned earnings survey was published, and we were finding out the results the hard way.
I would have expected it today, but even back then we didn't resort to panic (right away). "People have only started to notice the game," we thought. "We'll push an update and get back on track."
I finished my semester of teaching in February, so it was perfect time to get back to coding, creating all the neat little things I didn't have time to squeeze in before Christmas. It was a lot of fun, even making viral videos in the process (if you count one Reddit post and 5,000 views on YouTube "viral", which I don't, but it's still the most watched video on my channel, at any rate).
After I spent the aforementioned 71 hours coding the update for the game, it took me 113 more (that's one month of effective creative work) to run the marketing campaign, including making a new trailer (which flopped) and a special webpage with a promotion to drive traffic to our Twitter and Facebook page. I spent the rest of my time sending dozens of review request emails, organizing promo code giveaways, and replying to review comments and forum threads. If you just want to focus on your art and code, forget about running an indie game business.
The promotion went well (ish) and with over 200 people on our social networks (you gotta start somewhere) we promised a price drop to $0.99 when the update hit. The re-launch day was full of meeting nice people on our livestream and again it was fun, fun, fun. Enjoy it! That's what it's all about. If you don't love what you're doing, you're going to give up. Especially when the numbers come in the next day:
Monkey Labour weekly sales (v1.0 plus the first two weeks of v1.1)
We sold 215 copies in the first week and only 24 the one after. I was like, "Shit, we're right back in the long tail."
I was ready to accept that Monkey Labour was a flop. No one, NO ONE, decided to write about us. With barely over 1,000 units sold, I would be happy if Dawn of Play ever wanted me to work on games again, let alone allow me to send another email to a review site. Below you can see what my PR effort looked like -- if you ever wondered what kind of email to send out (or not, judging from the nonexistent results.)
My press review request email template
It's much better than the first version I wrote (the one where you get the idea to re-imagine the way you communicate with the press by sending a very personal story about how this game will touch your heart and soul -- yeah, forget it). But obviously these guys get tons of normal to-the-point emails just like this one. Result: our retro handheld homage would be left undiscovered by the wider public.
And then something amazing happened. I remember screaming and jumping around the university lab when I read the news: Monkey Labour got a great four-star review on the main iOS gaming site TouchArcade. Sales went boom:
Monkey Labour weekly sales (all versions)
The effect of a TouchArcade review proved the site's reputation. It's nothing like getting featured big-time by Apple or getting on the overall charts, but for a niche game such as ours it's been enough that I stopped feeling shitty about myself. I used the gained momentum and wrote a similar review request to other Metacritic-approved publications, landing a total of 11 critic reviews for the game. The final score of 75 made us the highest rated iOS app launched at that time (not that it mattered to sales, just to give you some perspective). My PR experience points poured in and I felt like I leveled up. I finally knew what I was doing.
Monkey Labour's combined press response on Metacritic