Claudia -
These "big bills" are an issue if you don't know they are comming and you don't factor them in (saving for them). The overall cost of running an EC120 we appear to agree is lower than a 44. So as the 500 doesn't have these big bills, what are the general running costs like? If you pay 5k for a 50 hr then it might be more expensive overall than an EC120.
Can you (or any 500 owner) post comparative bill details for 50 / 100 / 6 month for the 500? It is the only way we will all know.