Not really a deal because the prices of store specific for Mc Donalds (Springvale in my case).
And since the touch screens are new, it's possible that the person programing the prices programed it incorrectly and when you make some drink selections, instead of adding to the cost it's subtracting them instead.
In my case I ordered a Mighty Muffin ($4.75 by itself). Made it a meal $7.75. Then scrolled down to 'Sml OJ LSM' and it had -$3.35 on it and ended up reducing the overall price to $4.40, less than the muffin itself. And on top of that the computer told the guy to give me 2 oj's for whatever reason!
But like I said the prices are store specific and it's just a matter of getting lucky and knowing to spot to the subtraction signs instead of additions to see if you can take advantage of some pricing errors;.
Still too expensive. /tight
Nice find though. Enjoy 'em while you can! :P Thanks for sharing & caring (and potentially having someone leak this glitch to them earlier than might've happened naturally - there's always one, but hopefully not).