If you can get points that cheap you should go for it. More often the points rent for $20+ depending of when and where you wanna go.
Each to his own.
If I'm going to WDW no way am I staying off site. Just take the new Genie+ service and ILL if you don't stay onsite you are already 2 hours behind for booking Genie+ and buying ILL. You most likely won't get to try ANY of the more desirable attractions unless you stand in line for 2.5-3 hours

Plus you get earlier access to the parks when staying onsite.
But frankly I also like the resorts and being in the Disney bubble. A few years back I stayed at HGV while visiting WDW, and even though HGV is nice its just not the same when going to WDW.
I know that Bonnet Creek is part of the Disney friendship hotels and it should provide the same benefits as staying onsite, but still its not Disney.
There is a reason why most if not all Disney resorts are fully booked 99.8% of the year, its not because you can book something cheaper elsewhere because no doubt about it - you definitely can - but its still not Disney. People want Disney and they happily pay for it.