You'd have to address that to the OSC, but I suspect it's a tiny amount, not many people would cough £8 just to vote in a ballot.
I suspect it may not be as tiny as you think but then that is your opinion,and i agree not many would pay £8 in these hard times for so many,but that only adds fuel to the fire as there could also be many that would vote a yes vote if membership was free.
You and everyone else does not know if that would be the case.