Sharebuilder rips you off on stock prices?

I'm a new investor, and I think i'm being ripped off. I have an account with sharebuilder, and sometimes when I place trades there, the price they "purchase" the stock for me at, is actually much higher than the market even REACHED on that day. And i'm not doing anything but using market orders, so I really don't see how that's possible.

For example, I had purchased 75 shares of nokia stock when the price was like 3.83 a share. Later on, I purchased 10 more shares when the price was hovering around 3.02. It now says I own 85 shares of stock at a cost of 3.94 a share. WTF? Has this happened to anyone else?

There was also a case where i purchased Quicklogic, (QUIK) when the price was around 3 a share. (within the last week) I purchased 40 shares on the 13th of sept. 2012. It said I purchased them at a price of 3.49. That's my cost per share. That's ridiculous because the price didn't even reach that high that day. Not even close. Has this ever happened with anybody and is there something I don't understand happening here? Or am I being ripped off?

Stop doing market order and start putting a limit on your order. Stock prices fluctuate so much it will be hard to prove your broker is ripping you off. Just put a limit on your order.
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I agree with the previous poster, always use limit orders. If you are not satisfied with you broker shop around. I have yet to be dissatisfied with a broker as to performance of their platform. So I choose my broker based on the platform they offer and commission fee structure.

Check out their platform. I have not personally used them, but I have read a lot of reviews suggesting to stay away from them.