Shipping plus customs. I think someone must be growing them here but insects are a major problem in my limited experience trying to grow chilies. So perhaps the have limited yields. We don't get much variety in chilies here except what is imported or what is brought in.
Coming into Thailand I brought probably an lb of dried ancho and chipotle. There's no declaration form or need to stop at customs. Shipping on the other hand gets the customs people involved for some reason.