Pay to fly schemes do increase the threat level. A good example is the A320 accident in Kos. If you don't believe that, read the report.
http://www.aaib.gov.uk/cms_resources...JZ%2012-08.pdf If that pilot hadn't have been paying for his own rating, then he wouldn't have been in that seat. The airline exposed the passengers to increased risk to make money from pilot training.
Airlines who sell the pilot's seat are putting passengers at risk. They justify it through their training requirements but are training way in excess of those requirements because the pay to fly schemes are very profitable.