Wouldn't need to.
Firstly, most of these will be cult owned and operated (need to be to get the spells). That's a serious piece of competition to go up against.
Secondly, since we're talking about Rune Spells provided by the God, unsanctioned methods can just lose their ability to be cast ... Not in the God's interests, especially if measly little initiates are opposing the priesthood and temple.
Thirdly, for a group of adventurers, it's simply not worth the hassle... The amount of time, effort and energy to finally get that show on the road *efficiently and effectively* alone would be virtually impossible (without significant outside support - which goes against the "alone" bit).