Yes, they are right to do this. The operations of the flying club in any form is likely to have some fixed overheads that have to be defrayed across the entire membership. If you want a clubhouse, an internet connection, a coffee machine, a place to keep stuff, etc. It all has to be paid for whether or not anyone flies.
Whether or not a 'joining' fee is justified, is down to the club. Many organisations run on such tight profit margins that even the administration of a new joining member has to be charged for. However, I would regard any joining fee above £5 as excessive, unless the joining process delivers some exceptional value, e.g. a checkout on the club aircraft.
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