The first step to receive is the same signing up on the online websites to get the Authorization Code and it does not have a certain cost and each service provider receives some cost for it varied from 35 to 100 Euros and it depends on your luck! The second step is getting the visa stamp from Iranian Embassy that depends on your nationality and costs about 40 to 70 Euros and it is paid to the embassy. Of course, these all are approximate. In total, it does not cost too much; do not worry.