if i put a buy order in at $20......

[bitcon]

and the lowest ask price is at $17, does my purchase default to the lowest "ask" or do i get the BTC for $20 each?

[bitrain]

Lowest ask will work...

[MiningBuddy]

I guess it depends on the market, mtgox has an explanation https://mtgox.com/support

[chuckypalumbo]

I guess it depends on the market, mtgox has an explanation https://mtgox.com/support

This, it looks like you would get BTC at the lowest levels leading up to $20 until your order is filled. So you might get some for instance in the $17's.

[enmaku]

There's a handy calculator on the Market Depth tab of the Mt Gox charts on bitcoincharts: http://bitcoincharts.com/markets/mtgoxUSD_depth.html

Just put in how many BTC you want and it'll show you how much you'd have to pay at current market prices for the whole lot, starting with the low prices and eating its way up.