Im finishing a little game I plan to release for Android and PC, and Im considering how to get some profit from it. I dislike the idea of selling any advantages inside the game, as I think that the game demands to offer the same opportunities to all players so they can compare their results (thats why Im not using procedural levels neither). My first idea was to sell it for a small price (0.99-1.99) if the demo had some success, but my cousin, who lives in UK, says that nobody pays for games anymore, and indeed Google Play is full of free games.

Not sure if in-game ads could be the solution, I think I have some margin to place ads in the transitions between levels. I hate disrupting gaming experience, but if players dont want to pay...

Make it high quality, capable of standing shoulder to shoulder with the competition. Make it free to play. Sell cosmetics in game. Put unobtrusive ads in it (e.g. offer a video ad upon death to earn an extra life). Put analytics in it. Soft launch it in a small country first and analyse the data. Find out at what point people stop playing and polish whatever is causing them to give up. Get in touch with Google and Apple in the lead up to launch and get them to feature you on the front page (again, be high quality so that they do). Alternatively sign with a publisher who will take 50% of the earnings in exchange for millions in advertising. Launch globally at the start of your feature window. Get a million downloads per month. Now you're a semi-sucessful small mobile developer.

Is there a question in there?

I think you are asking for a catalog of ways to monetize games, for which there are many articles that can be found by searching.

Sorry, I think I didnt expressed clearly.

My question is if I have no other way than ads. But Hodgman reply has been clear enough.