Let "x" be the cost in dollars of the Taco Grande Plate.
Since twice the cost of John's Taco Plate equals the cost of Mike's Taco Plate plus added items, then 2x = x+2+4+2.
Simplifying the equation, we get 2x = x+8.
Subtracting x from each side of the equation, we are left with x=8 dollars as the cost of the Taco Grande Plate.
Thus the combined total cost of Mike and John's lunch is 8+8+2+4+2=<<8+8+2+4+2=24>>24 dollars.
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