"What do airlines really think of pilots paying for actual line experience?"
Well, I can tell you about Iberia in Spain. A friend of mine was called for interview some months ago. Min requirements were 500 hrs on type A320, he had about 800 hrs on type as he paid for TR and 300 hrs of actual line experience before being employed with a Turkish A320 operator.
Needless to say he was turned down at interview with the training captains as they didn't want "flying prostitutes" in the company.