I know some people do well making a website on selling cheap stuff that are below $10, and I also know people that focus on promoting appliances that make less sales but higher commission. What's your preference when promoting Amazon products?
I wouldn't really categorize it as that. I would find an item that is frequently ordered, then use my data on the orders, not price
It is best to have combination of both high and low price items. Low price items sell easier, so you can reach higher commission rates faster. But the high price items will be the ones which will help you have a respectable revenue income stream. So my advice would be do both, or you can focus only the high priced ones if you want that because many times you will get sales not related to your niche. It is just how people surft the internet and Amazon.
I do exactly as @meepmeep says - promote lots of cheap products to boost commission rates, which in turn gives bigger commissions on the higher priced items i promote