You ordered two complete meals (a drink, a side, and an entree), you probably got it in 30 seconds, and the total was less than the cost of comparable meals at virtually any restaurant. And you were aghast? ....You are aware inflation makes things cost more over time, right? 2% per year means things cost 10% more after just 5 years

That is precisely the problem, you look at the inflation and compare it to what you payed 5,10,20 years ago and your either getting less or paying more than that inflation. Average price inflation of a big mac in the US for the past 25 years is 4% versus average CPI inflation of 2.29%. So instead of increasing in price by 65% it increased 166%.