Got offered a better deal after agreeing to one with another dealership

Am I an asshole for contemplating going with another dealership to sign a lease if I already accepted and ordered a leased X5 only to get offered a way better deal than my current sales person? Been dealing with this guy for 10 years now and in my view he could have done more to get me a good offer in the first place. How do you guys value relationship vs saving a few bucks on a car?

I haven’t really signed any offer on paper just verbally.