It is profitable as the running costs are very low, but currently my income is only around $1k-$2k/month. It started as a side-project but I have been working full-time on it since last year when the gaming company I was working for went bankrupt.
Being a dev I am too focused on product and I always want to "fix one more thing" before marketing it. As my savings got lower the product got better, I think I am now at that point when I can start finding customers without having to worry that "maybe my product is not good enough".