@Arthas429, not sure how you approached it, but you need some fundamentals laid out so people that are very knowledgable on this forum can help you out.
@MurlinatoR is awesome. I can give $.02 worth also.
That said, which model (MSRP) are you purchasing?
I would then suggest you start by negotiating down the MSRP down. Around the Pac NW most will take $2k off easy now.
Make sure you know the Lease Cash figure for your model and apply it.
For an example, let's go all-in and go with a GT2 AWD model. $49,200 (+ delivery $900) = $50,100
You negotiate $2,900 off the sticker to a cost of: $47,200
The lease cash for this model is $7,200 (so take that off the $47,200)
This leaves you with a Capital Cost of: $40,000
Now, take the sticker of $49,200 * .52 = the Residual Value of $25,584 (the price you can buy the car after the lease term).
Now we can figure out what your 36mo monthly Rent Fee should be!
Take the Capital Cost ($40,000) and add it with the Residual Value ($25,584), which = $65,584
Now for your interest, called the Money Factor. The best rate you can get with a great credit score (700+) and the dealer not throwing in a bit extra, which is allowed by Kia Financial, is .000196.
$65,584 x .00196 = $128.54 in monthly interest.
Now, take the Capital Cost of $40,000 - Residual Cost of 25,584, and you get $14,416.
Divide $14,416 by 36 months = $400.44 a month.
Add the $400.44 to the interest of $128.54, and your monthly lease fee should be: $528.98 per month, with a Residual Value of $25,584 to purchase.
NOTE: You said you had 45k miles baked in. that is 5,000 miles MORE per year than what is built into the non-altered lease program with 10k miles a year. I do NOT know how to factor that in.
I believe each mile is $.20 additional. Thus, $.20 x 15k = $3,000
$3,000 divided by 36 months = $83.33 a month more. I'd just make sure they are not backing that $3k INTO the Rental Fee and thus adding interest to your milage! Ack! That would be horrible, but I can see a dealer doing that instead of just straight adding the fee w/out interest to the monthly lease fee...
I would also suggest that adding more miles CERTAINLY changes the Residual Value. Thus the .52 multiplier of the sticker is going to be lower... Or it SHOULD BE! Another 45k miles after 3 years instead of 30k miles? Hmmm... I have no idea. This is where the dealer "could" play games. I would assume it would be worth 46% or so?... And that changes the ENTIRE equation.
Hope this helped! Good luck!