As long as you don't get too crazy with the discount, you should be able to get them to lower the price a bit. On a new car, dealers usually make more money from the financing than they do from the sale, but used cars can be different.
OTOH, since most salespeople are on commission, it can be very difficult to turn down a guaranteed sale. Just make sure there is a bit of room for them to make said commission.
See my perception is that used cars are even more skewed towards financing profits -- at least in the US, used car loans almost invariably carry higher interest rates. The 0-3% interest rates for new cars are almost unheard of for used cars, at least traditionally, because they're essentially a marketing expense subsidized by the car maker (the OEM pays out of its marketing budget to its financial arm to subsidize the below-cost loan as another form of incentivization).