We started flying WN in 2016 when we learned about CP. We have never paid cash for the entire cost of a WN ticket and we use WN 4 - 6 times a year ( 8 - 12 R/T tickets) but I have "paid " for at least part of ~ 10 tickets via LUV vouchers we have received as compensation for delays.

I would never pay for a WN flight unless it was MUCH cheaper than DL. DL also flies NS to all of the cities ( MSP to BDL LAS, RSW, TPA) that we travel to whereas WN almost always requires a stop on the way