Seems like a fair price to me.
I'm in a 172M share, 1973, many more hours TT & similar instrumentation. I effectively pay for my 1/8th share, £83 per month and £49 per hour wet. That does include overpriced hangarage, though.
Do all 13 like to fly at the weekends? Its a big group and availability would be my concern.
Good luck
-bcfc