First - find a fair price for the X7 you want, say $112k on a $117k MSRP.
Second - then say, I can sell to Carvanna for $25k
, I save $1.7k on taxes so will you take $23.3 on trade-in? The deal is done if you can do both.
Personally, I'm willing to pay a little more to go local. I don't want to drive to pick it up, better service when buying and you always get a loaner when needed.