Does Google allow you to link from your Adwords ad directly to Amazon or Ebay pages with your affiliate ID in the link? I'd like to know if I can bypass making a landing page and just have the customer go straight to product page to buy.
adwords doesn't allow direct linking to merchant sites. you must have a landing page as your display URL and landing page URL has to be on the same domain
yes you can use your affiliate link as your destination url but the CPC will be higher than while using a good optimized landing page.
I've linked directly as an affiliate before and had no problems at all. I don't know higher CPC, I have no way to measure this.