An order of paint costs about $200, and lasts me about 50 paintings. Traditional being expensive is a meme. Paint isn't diamonds, it's not that expensive. And if it is you can just get student grade which will literally costs you about $45 for a full palette of colors.
Painting is 99% drawing, if you can draw you can paint with anything. You could paint using your shit with the brush between your toes, it's just adding color to drawings.
I just order better quality paints because they feel good to use, I could be using crappier paint if money was tighter, and still sell them for the same price. Cost of materials adds up over time but it's probably just as expensive to do digital art as it is traditional, digital probably costing a bit more depending on what you're buying.
If you want to paint thick, buy cheap paints, if you want to buy more expensive paints, paint really thin and make it last. Either way it doesn't run you that much.
Traditional artists end up spending the most money after a painting sells, either to a gallery (50-60% in some cases) or to ship it somewhere, or the cut the website you're selling it through takes.
The supplies are the supplies, they cost money but so does food, and electricity, and water.