I think it all depends and is a personal preference. I rented a reservation last year to someone and charged $13/pp for my BWV points and $11/pp for my SSR points...very close to the 2X MF you mention. For me, it was an acceptable rate. If I ever have extended family use my points, then I charge right around MF. In all cases, they were points that I knew I could afford to rent out and were not needed for upcoming trips...so what I got helped to reduce what I had to pay for my 2018 MF's.
As stated, whatever others are willing to pay as well as how fast you may want to secure a renter will play a role. If I get in the situation where I have points again to rent, I won't hesitate to rent at around that same level.