Not sure how much your trade is worth, but assuming it's $7K or more, a better use for the money would be:
- Apply MSDs (Multiple Security Deposits). You get 0.00007 MF reduction with each SD, up to 7x = 0.00049. Net MF becomes: 0.00146
- Note: cost of each SD is your lease payment rounded up to nearest $50 after applying MF reduction
- Pay the sales tax up front with some of the trade money instead of rolling into the lease. You will save ~$150-$200 of interest on the sales tax.
With the above:
- I get a net savings of ~$1500 over the original scenario of rolling taxes into cap cost.
- Putting $7K into cap cost reduction wil lower taxes, but still rolling the remaining taxes in yields ~$1000 net savings (Lease cost + $7K trade).
- The extra $500 savings of the MSD route comes from savings on the interest rate.
BTW, I am in Texas and looking at going from purchase to lease with an F30 as well (I have an '02 330i) and the 7xMSD is what I am going to do. Also, I doubt you will get any dealer in Houston to take the $500 over invoice deal on any car, much less beand new F30 - dealers in Dallas are the same. But, let me know if you do.