4k seems really low for a trade value. Check autotrader in your area. Here, there is a 2001 325xi MT advertised at $10k, and a 2003 at $11k. Seems like you might be trading at wholesale, but buying at retail. Neither price matters, just the difference.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue