I think you can make a very good living and beyond from the sales of your prints, lets call your prints art, and the selling of your art business.
The art business like any business takes an incredible amount of work to be successful at, whatever work/time you put into making your art; times that by 10 and add infinity to make the business side successful. In this regard, it's no different from any other business.
Working smart and working with a plan will not necessarily ensure success, working stupid and working without a plan will most likely ensure failure.
I have been earning a very good living for the past two years selling my prints, my business continues to grow and evolve, I have been very lucky to some degree, as I have a great location and solid cash flow, which has allowed me to develop, refine and expand my business model.
I don't necessarily think you can quantify initial success or failure; or always monetize your results every, business has tangibles and intangibles.
Making money from your artwork is not easy, it can be done with varying levels of success depending on a multitude of factors.
I think the biggest factor confronting your success is your desire, and your desire must be truthful and fearless.