are they comparable? can I make the same amount of revenue using google advertisement and my own website vs ebay? how can I find out the estimate revenue of the website that are selling sunglasses and that are placing their ad there?
they are very different ways of making money. Both can drive sales but eBay is far simpler. Adwords is harder but can drive incredible traffic. Use spyfu.com on your competitors keywords to get estimates of click costs and daily click rate.
Both tools are used for traffic generation but Adward is a bit difficult as compare to eBay but it is helpful to get huge traffic.
Even though they are completely different I want to go with AdWords. Anytime! It is a bit risky, but results can be really really huge if done correctly!
it all depends on your approach. It's like asking the question which is better, Crab Legs or Lobster? Both are viable, but if you don't have the right strategy in place you will fail both places. Good marketing, copywriting, and strategy works everywhere.