am electrical draw on 2003 BMW 525i

just had a new alternator installed, but there seems to be a draw somewhere still and its draining battery, how much would it be to fix or is this common?

Asked by for the 2003 BMW 525i
Unfortunately it's impossible to give an estimate on most electrical problems.
You need to pay for clock time.
In this situation there is a parasitic draw, which means one or more of the control modules won't go to "sleep mode" and keep consuming energy. Sleep mode should start in 16 minutes after the car is locked and the security system is armed. That's when the remaining consumers (beside few circuits) turns off.
On your BMW in sleep mode there should be only 40 milliamps drain.
A technician has to put the car to sleep mode with an OE diagnostic computer (otherwise he needs to wait 16 minutes each time of system disarm) , than start to check the circuits, first the primary and so on, until he/she finds the "hot" circuit with the consumer is still on.
So now you have an idea of what has to be done.