I'm actually really impressed with the amount of money you've earned from a picture swapping game! I think you've done a good job identifying a niche (HTML 5 games) where you can deliver something quickly and at low cost. As you get better at producing games with Game Maker and improve your Javascripting I'm sure you'll grow your earnings.
Absolutely, and I've been noticing an upwards trend. Some of my recent games have done exceptionally well given their simplicity...games that took me 30 hours to make in GameMaker Studio have made over $2500+ and to really push the limit I recently made a game in 9 hours to see how it would perform. So far, so good.
I think the key to making money online is to try
everything. Eventually something clicks