I feel like maybe I'm not explaining what I was trying to discuss very well or something because it seems people are missing the point. I understand why they don't regularly repaint coasters, that would be very costly.
No, the paint I use is NOT super expensive and still doesn't fade as fast as what is used on coasters, which I assume is expensive paint, so what makes one fade so fast and a cheaper paint doesn't? That is what I am wondering. I have used cheap acrylic latex paint on cement statues and so far seems to not fade at all after many years. It needs repainted for peeling before fading so I assume they wouldn't use that kind of paint for similar reasons- peeling.
I have used a spray paint from Walmart that is about $6 a can and doesn't seem to fade after many years and being exposed to the elements, but I painted plastic with it, not metal.
I personally think that it could have to do with the metal heating up to high temperatures in the sun compared to a cement staute or plastic lawn chair that is causing the rapid fading on coasters. Hopefully someone else will understand what I'm trying to get at and be able to add something constructive to the conversation about what causes roller coasters to fade faster that other painted things exposed to the elements.