Smart Key issues/ Options for replacing Smart Key

So the Mrs lost one of her 2015 Highlander smart keys last year and is now having issues with her only remaining key this year. We were quoted around $600 to replace it. This would be the cost of the remote and programming, which sounds like the largest portion of the cost.

Her current key, gets alerts of low battery every 2-3 weeks and we replace the battery. I have a few dozen of them now. It also consistently says "key not detected" at times when the passenger exits the vehicle. (I know, WTF?) Even though the key is in the cupholder. 55000 miles on it.

Has anyone else had key issues? Could she use an aftermarket key? Is there a more reasonable option? Has anyone been quoted this much for a key replacement? Has anyone had theirs replaced under warranty?

 

Take it out of the cup holder....
Put it on your person, in her purse on the pass seat and try. Any place but the cup holder..