Can somebody please explain this to me?

Seems to me that there are alot of systems that people use that involve pre post prices.

Now on big events such as the Melbourne Cup, I believe that you can actually bet on the pre post prices. If the horse doesn't make it to the races then you have done your dollars.

Now often people refer to getting the pre post prices from the newspaper. Now if you can actually bet with the people that are giving these prices, then all is good.

I always thought that these newspaper prices were just somebodies opinion of what they predict the market will be.
Do these not vary from newspaper to newspaper?

Now this is confusing to me. Are they not just somebodies opinion? I mean, if you look at the trots pre post markets in the Herald Sun ( I think done by Hutchison? ) he singles out his best bet, and his best roughie.
If all the prices are not just his opinion, then how can he know the best roughie? If he has rated a horse at 20-1, then why would he choose it as his best roughie? Surely if he liked its chances, he would rate it a lot shorter.

Now if the prices on display are an actual bookmakers price, then maybe he has rated it as a $4 chance and knowing that $20 is available, it is his best roughie.
Although I don't think this is the case.

If you can actually bet on the prices shown in newspapers then please feel free to stomp all over me, but if I am right and these are just somebodies opinion, then I think that anybody that bases any sort of a system around these markets is really kidding themselves.