If anyone reads this for medical advice (and I really hope they wouldn't be taking advice directly from HN without any filtering), you don't combine them in equal proportions.
Meanwhile 500mg is, I believe, more than they combine with opiates and acetaminophen does lead to death via organ failure on the order of hundreds of people a year. I was curious why they weighted the acetaminophen proportionally so much higher than the ibuprofen.
Unless they need to be prescribed in ratios that can't be achieved reasonably with the cheap OTC pill dose sizes, it's not clear to my why I'd want a combined bill instead of just taking separate pills.
Taking more than one pill is less convenient, but except for people who have trouble with pills in general I doubt they would want to pay more for that convenience.
Even in the case of fairly high doses, it is not too bad. A few months ago, for example, I somehow managed to get a painful rotator cuff injury while sleeping (no idea how), and my doctor told me to take 1000 mg Tylenol every 8 hours and 800 mg of ibuprofen every 8 hours. At the most common OTC strengths, that would be two Tylenol pills and 4 ibuprofen pills.