Price determination

In this video Martin explained how anyone could bet on selected prices to get a better picture of which prices are best.

Why is it not possible that anyone can select his own price he thinks is best instead of betting on a preselected price ?

Besides that i would like to know what vitalik explained at the end?
I didn’t understand anything.

So it is possible to add new suggestions later.
However - to make it practical and user friendly you should not have too many. Vitalik was suggesting to make a “binary search” for the perfect price. So the question would be should we do a price of >$10 or <=$10. Lets say the result is: <=$10. Then you would ask (automatically) >$5 or <=$5. Lets say this time the result is >$5 - then the next question would be >$7.5 or <=$7.5 and so on until the range is narrowed down far enough.

We are working on all this stuff - one first example could be to sue a prediction market to figure out what amount should aim for in their token sale.