Knowing past eBay item auction prices is a great indicator on what you really should be spending. You can actually see past listings and sales on eBay through what is essentially a hidden search filter. Here is how to view the past history for an item on eBay:
Type in the item that you want to see past sales history on in the eBay search bar. Hit search.
In the left hand panel that has the search filters find at the bottom “More refinements..” click this
Next a window will pop up which is just another display for search filters. On the left of this window is a scroll bar, go to the bottom and select “Show only” then click on “Completed items” and “Sold items” finally click the blue Apply button at the bottom right.