What is Realistic?

What is a realistic time that a typical athlete can aspire to in an Ironman Triathlon? When it comes to Hawaii it seems like the 1st place finishers and a handful of other pros are finishing between 8 hours 10 minutes and 8 hours and 30 minutes. I think the top women pros are finishing around an hour later. So where does that leave me? Sure most people would say, “How can you tell when you have never run an Ironman?” While that is certainly true, what I am really looking for is a time that a typically athlete can shoot for and realistically attain? Sure the number is ultra-subjective and not really good for much, but what a number like that does is provide a little perspective. For example, when I was in high school I read a book by Ron Daws where he outlines training plans for runners of different competitive levels(phenomenal book). In that book he breaks down, by distance, realistic times that a healthy person can run given a great deal of patience and hard work. The one distance that jumped out at me was the mile, where he stated that a male that works hard in training and avoids injury could realistically run a mile in 4 minutes 27 seconds. So my question is, what is an attainable time in the Ironman? Not for the pro athlete but the everyman like myself? There are days where I think that I am going to really struggle to finish and there are other days when I think that I could run under 10 hours. Why can’t I run it that fast? Why can’t I run it faster? Sure I am in my mid-thirties but I still feel pretty good and I am working out hard. Maybe I could? To quote Steve Prefontaine from the movie Without Limits, “l won't know that till l get there, and I’ll figure it out then.”