One good way to buy from Lenovo is to go through corporateperks.com. Very simple and you get these kinds of discounts all the time. We bought our last couple of machines this way and got a very nice price. (No affiliation with them other than a happy customer.)
One way to buy Lenovo is to google for Lot of X on ebay.com where X is about 3 years old. The off-lease deals and lots of great machines you can find is amazing.
Indeed, I got a top spec x220 for about 450. It was about a year old and still under extended warranty, and practically brand new when I got it. Buying a new Lenovo is worse than buying a new car in terms of depreciation.
Often those discount codes are advertised quite blatantly on the manufacturers site. A lot of PC Manufacturers tend to have long running discounts on their website that will save you a lot over the original retail.