I'm a little surprised the store didn't pursue your dad for deliberately damaging merchandise (that knife mark). This could have backfired...

Also, for anyone OK with a floor model, check out used office furniture stores. I got a high-end Steelcase chair for $300 as a replacement for the identical one I'd purchased new for $1100 a decade before. This one had almost no wear; I think it had been in an unused conference room for a lot of its life before me. These stores don't advertise to people like you and me - but they're happy to do business with us.