It varies. Just depends on the mfg. and product. Best deal he got me was last thanksgiving. Got a 55" LED LG tv for less than $200.00. On things like cameras its usually around 40%. I know when I was looking at a new case for I phone he got me one of LifeProof cases at about 35% off and he gets really good deals on their protection plans. He got one for 3 years on his brothers tv for like $12.00. On other cell phone and gaming accessories he pays next to nothing
I pricematch at Best Buy all the time for misc. things from appliances to computer parts. More of the later. usually when I don't get an approval. I come back another day or go to a different BB and try again. It's a hit or miss on approvals because some people are strict and some people are very cooperative.
Last year around this time, I was able to combine price matching to Fry's, use a student discount and also a USPS mover's code at Bestbuy to get a Mac Book air for 625.00 before taxes. You just need to find someone who's willing to do it.