Depends (to answer stevie's last point) on the local group - ok Northumbria Blood Bikes, we insist on riders having an advanced ticket. But then we also don't allow use of private vehicles, and pay for the fuel in the charity bikes - so overall, it's going to work out a lot less than not doing iam/rospa, but buying your own fuel. Some of our riders are doing 200 miles in a shift, doesn't take many shifts before you're better off.
But of course, it's not about the money - the satisfaction can be (is) huge.