I felt the same way you did when I first started bidding on ebay, but I quickly learned the ropes. I also learn that a lot of times the kit could be found at the same bid price or cheaper from on-line hobby store. Found it amazing that shipping charges greatly varied from vendor to vendor located in the same state. I can't help think that they are using shipping to increase their profit.
If I am looking for a kit ebay is just another tool in a attempt purchase it.