When I chopped in my mk 7 GTI (one year old) the price one of the dealers gave me was so laughable - especially as they had a mk 6 GTI right outside the windown on for 4K more than they were offering me for mine - I also walked out (after pointing to the one on the forecourt). Just cause they're in the selling game does not make them good sales people!
They will always try to make £4k on a nearly new VW performance Golf if you let them. That is perfectly fine with me if I get 12% off the new one - it is hard to get a great deal both ends. They will want 15% margin in any used car after a bit of haggling. For this reason it's best to sell privately for £2k less than forecourt prices and everyone wins (except the garage), if you can put up with the tyre kickers and time wasters.
Oh yes, I've no problem with them making a profit - but this particular salesman wanted to offer me 16k for a one year old fully loaded GTI PP and then offer me zero discount on an R. I told him to jog on!
Had the same experience today, left my car in for its first service, thought I would price a new GTD DSG with a few options. So price came in at £30,500,
Sales guy gets on the calculator and says, yes so it will be £11k to change you current car (2014 GTD), that was based on a trade in of £19k (which was ok) but only £500 discount on the new car, didn't even look like he wanted to try and deal, if he'd of been around £7-8k to change I would be tempted, but £11k NO THANKS