Well, low priced doesn't always mean less. If you send them good amount of traffic people will buy something else beside cheap items as well.
What I have done is make in Wordpress reviews for more expensive items is to make a lower priced Related Items, or accessories to the expensive items. This should help, so if they aren't totally looking for the expensiv parent item, then there are all of these items related to the category that hey could be looking for.
Well lower priced items do not tend to give worthwhile commissions but they definitely help in increasing the commission rate (which is tier-based) for high ticket items.
It is worth it. One of my first amazon websites promoted $15 products. It sells like peanuts.. lots of them. The site was not even in Google's page 1.
I would add to this that popular items add up faster. Also, perishable items also work well as do rechargeable batteries.
I always run a few sites that promote lower paying items simply to get my number of sales up faster and into the higher percentage bands so when I get more commission on the higher priced items. Cheaper items can sell a lot faster and often people buy 2 or 3 cheap items at a time. So yeah, its definately worth it, but only if you combine it with sales from another site that sells high priced items.