For what I know during the normal stock exchange you sell to the highest price and buy to the lowest.

Suppose there a stock EXMPL, and some people want to buy and other want to sell.

Now put all those people in a line with the seller facing the buyer sorted by price.

So in front of seller line there is the one that want to sell at 100, followed by the one who want to sell at 101, then 103 and so on.

In front of the buyer line there is the one who want to buy for 99, followed by 98, and then 97 and so on.

In this situation no exchange is been made because they cannot agree on the price.

Now suppose that someone is betting heavily on EXMPL and decide to buy 100 shares at 102$. It goes in the first position of the line and ask to the one who is selling at 100: 1> "how many share can you sell me at 100?"

2> "75 share for a total of 7500$"

1> "Deal, here the money!"

Now our buyer goes talking with the second of the line...

1> "how many share can you sell me at 101?"

3> "100 share for a total of 10100$"

1> "I only need 25 for a total of 2525$, here are the money"

2> "Deal, here are the share!"

And the 102$/share guy left.

At this point the last tick sign 101$ which is the "price" of the stock, note that nobody is buying anymore at more than 99$.

During an IPO I wouldn't expect much difference...

In my understanding the money "left on the table" are just the one needed to rise the price...

Am I missing something?