I know, I'm comparing old with new - it used to cost 13 POW for an average person to be able to fly, now it just costs 1 DP.
My point about the magnitude is, allowing an initiate with Pact (Orlanth) 11% (POW 10 + 1 DP) to fly is quite generous - making it higher Magnitude would require a higher Pact skill. Maybe Magnitude 6 would not be excessive, so you have to get your Pact up to 51% before you could fly, and allow an additional 6 SIZ per Magnitude above that.