It sounds like you were not charged landing nor parking for the unplanned stop, and it sounds like the club did not charge you for the loss of revenue while the plane sat elsewhere, unavailable to hem for other rental. So two people spend x hours going to get, and returning the plane, so cost for their time, the operation of the plane you had been flying, and either a car or another plane, and if they flew, they might have been charged landing and parking at the other airport. Whether what they charged you was fair or not is based upon the charge relative to the cost to recover the plane. That would be a discussion you could have with them. However, the fact that they charged you something is fair, it cost them something.
Your decision to divert, or continue to your planned destination should not be based upon cost, but rather life. Over the years, I've had to divert a few times, both in rental planes, and my planes. It's your choice to fly, so the risks and cost of an unplanned stop are yours too.