Looking at Costco's website you may be able to figure out some of the normal prices, at least the items they have on the site.
For example:
They have a Pentax 6.0 MP camera on the site for $179.99. At $50 off that's a good deal, if it is the right one.
The: Philips 32" LCD HDTV Television - $200 off (on site $1,499.99)
KitchenAid Stand Mixer - $40 off (on site $269.99)
Speed X. Razor - $20 off (on site $89.99)