The dealers are laughing at me aren't they?

Hi everyone, glad to part of this amazingly helpful forum at last.

So I am the proud owner of a E90 330i LCI steptronic, exclusive pack, with paddle shifters , xenons, hi-Fi sound,sunroof.Titanium Silver.Just rolled onto 44000kms and she is purring like a kitten up here on the Reef in Joburg.
Loving the car over the past 4 months but decided to test what kind of trade-in the dealers were willing to offer me in order to hypothetically get into an F30 m-sport.
Trade value on my car is around R320k if all my research is correct?
Average offer from BMW dealerships in Sandton averaged around R250k - can this be right or are they having a laugh?
For fun I went Mercedes and the offered me R220k...
Realistically I will be looking to trade in next year as motor plan is up around then.
What value, realistically, would I expect to get for my car if I do only another 6-8000kms in the next year?
Are the dealers really giving me so much below trade or is that the state of the market for my class of E90 right now?

Thanks in advance all