slippage on big trades

I read some comments in another thread on this forum, It was a discussion about ecn's etc.

Now someone mentions that it is nice/good to have a slippage of 5 pips on an order around the 50M.

If that is true, does this mean, you just have a huge slippage on your orders ?

I think of two possible scenarios (both on ECN style broker)

 

1. You take a long position and have slippage of 5 pips (the price goes higher), after a while you sell and the agian you have another slippage (the price goes higher) this time it was in youre favor
2. You take a long position and have slippage on buying and selling both 5 pips.

Scenario 1 is OK because sometimes you are lucky and the slippage is good (you buy long and price is dropping)

Scenario 2 is not good because the slippage is always against you.

I think the second scenario is more likely to happen because if you are buying and there is not enough liquidity the price must go up ?

However more than once my logic was flawed, therefore i would like to ask you guys (and girls).
http://cdn.forexfactory.com/images/misc/progress.gif

ps: posted it before in the rookie forum but i dont think the thread has a future there because i suspect the people that have a lot of experience with big orders are not there ( but again could be wrong)

If a forum admin read this, the thread in the rookie forum can be deleted.

Overall scenario 2 is more likely if you trade really, really large.

If your orders are too big to get filled at one particular price than you don't experience slippage, it's actually more a case of "moving the market". And that is exactly how markets work ... if there is too much demand at one price, price has to move up or down. So, if you trade huge amounts you can't really scalp for 5 pips. (but don't worry, you need slightly more than 50mill to move the market substantially .. well, it obviously depends on the currency pair, but the majors can usually take a 50mill order without causing a 5 pip move)