I have always used the advanced search feature to track trends and ebay market pricing. All the items I have sold I have gained an average of 700% profit. This is also including shipping methods and method of payment for shipping materials. With my Paypal debit card I get 1.5% cashback on all purchases which helps to offset FVF fees.
As far as buying goes, if you can wait for the market to be saturated that is the best chance to get one for very cheap. I don't even know why seller saturate a big ticket item, just dumb.