First of all - I suppose it should be very cheap. So, real humans will not pay much.
Second - why do u think that websites are meant to be free? They provide some service, so its a rather strange that the internet is so free (in both senses). I think, this freeiness is allowed to greatly speed up popularization. But for me is obvious that it can demand payment for service.
And third - service owner really meant it to be free, I don't see any problems with this in my idea. It can still provide free service.