I have purchased stickers that I couldn't find elsewhere -- Pocahontas, Kim Possible, Hunchback of NotreDame, Hercules, Lion King -- this was before the explosion of Disney Character Jolees or EK Success embellishments. I have also purchased a few lots of Jolees -- you can get a really good deal on these at times. The last set I bought averaged out to less than $1.50 each. Of course, if you don't need the whole lot then it is not a good deal.
One Christmas my sister bought me the upper and lower case sizzix fun serif set for $100 including shipping. It was used, but in perfect condition. My dad got me a 225 count of monochromatic Bazzill 12x12 paper at a good price.
When I shop on ebay I usually set the list to "ending soonest". I don't get involved in bidding on anything until it is less than 24 hrs until the auction ends. I also set a price limit for the item and strictly adhere to it. I don't want to get caught up in the moment and overpay for an item.