Is it right, according to the Vinaya, to charge for Dhamma classes? (I'm not talking about donations, but a fixed amount per class one has to pay)

There is a Buddhist Centre close to me that charges circa USD8.00 for Dhamma talks, in one hand I don't like the idea of any religion charging people because poor people will not be able to participate, but on the other hand things are expensive here and they need to pay the bills, my country is not Buddhist at all so running a centre here only on donations must be very hard. So, from a Vianaya and Buddhist ethics standpoint, is that allowed?