heres the case:
I sell an index option Call 400 for €3400
I buy 3 index options Call 500 for €900 each.
profit formula (x being the Index at the enddate):
-1*3400+(-1*(x-400(with min 0))*100+ 3*900+(3*(x-500(with min 0))*100)
the cost to take this position is -1*3400 + 3* 900 = -700 this...