For my Lariat, I paid $50 for the old key from someone's totaled Ford Edge on ebay. Programming was simple and took 5 minutes. Unfortunately, there are a couple of things that make this harder for you:
1. You need 2 keys to be able to program a new key. Since you lost 1 key, I assume you only have 1 left - therefore only a dealer can do the programming.
2. Since you don't have push button start, the key needs to be cut.

So the key for you still costs ~ $50 on ebay. Maybe you can save money by buying the blank key on ebay, but I don't see any way around paying for 1 & 2 above.

 

Check around for locksmiths. A locksmith in Waukesha charged me $125 for a 3rd key for my 2015, the flip-out key with remote start. He also has the software for older Ford's in case you don't have the original two to allow programming, possibly will work with the 2015. Ace Hardware stores are hit or miss, I couldn't find any around here that could cut these keys. Griffin Ford in Waukesha wanted $250+.

PS - if you have the two factory keys you can program your own spare keys if they're already cut, no need for plugging into the truck with laptop or software. Also, I was able to program new keys into my old Ranger with Forscan, that might be an option for the 2015+, not sure.

 

I haven't been around Ford long enough to figure out what they call it, but when I said keyless, I meant you push the button on the door handle to lock, and just touch the door handle to unlock, as long as the key is with you. So what you're saying seems excessive. That style of key, without the features I just described, ought to be more in the neighborhood of $150. The crappy thing is that if you lose one of the two sets, you kinda need to get it replaced, because if you're down to one, and you lose it, you gotta get the car towed to the dealer.

 

Just to be clear, if you buy a third key used from someone, does it at least have to look exactly like the ones you have? And then is it fine regardless of which Ford it came from? And as long as you have the original two keys, you can program the third yourself? Using just the three keys and the truck?

See, and my wife wonders why I spend so much time in a forum like this?

Mike Todd

 

I'm going thru this now myself as I've seem to have lost 1 of the 2 keys to my 2017 XLT. Turned the house upside looking for it and can't find it. Was thinking of buying this:

http://www.ebay.com/itm/NEW-OEM-15-1...IAAOSw65FXtJ-M

Then having the dealer cut it and reprogram for about $115.

 

If I can't find it again at work today, I'm going to take my chances on a $50 key off eBay and have the dealer cut/program it for me