Ok, now it shows the correct fee for me at BitStamp again - looks like it needed some time.
Bitstamp API is match slower than Mt.Gox and BTC-e because of 600 requests per 10 min limitation.
There is many types of requests: Account Info, Open Orders, Depth, Last Trades, History.
They only can be send one by one. This means Account Info updates with interval more than 5 seconds.
And Some of them (Depth, Last Trades) contains a large data, and API does not allow to limit it.
This means some requests takes a time 1-10 seconds some time. And update interval 1 second means interval between requests excluded their processing time.
I wan't to develop server to collect Depth and Last Trades and bring it to program in single connection.
This means there will be only Account Info, Open Orders and History requests send by program, and depth with trades will arrives realtime.
It will maximize speed. So keep tracking updates.