I spent $50 a year on wallpapers once as a monthly subscription. It was to support an independent artist that hand painted video game scenes I enjoyed, produced 1-3 new paintings per month, granted access to his back catalog, and the deliverable was high quality scans I could download and use at my leisure.

Since he is an artist, and you could feel that each painting took weeks to complete, I felt justified.

Never had a desire to pay for an app with generic wallpapers though, or to financially support someone who generates my annual salary per sponsorship deal.