Comparing purchasing prices is a bit of a vanity game. Mine is bigger than yours etc. I only use the one dealer for BMWs. I know them, they know me, I like their shop and attitude. If thats worth a grand over 3 years, so be it.
I m the same with retail shopping during sales. I hate shopping in crowded spaces so much, that not saving 30% and buying exactly what you want in the luxury of no crowds a week after sales is worth it for me. Horses for courses as my Welsh gran used to say.
I have a friend driving an expensive car at over £80k new whose depreciation alone is something like £100 per day, who will seriously drive an extra 6miles to buy 5p a litre cheaper petrol. V nice guy, smart professional etc. some people are wired this way.