While these price examples sound very reasonable to me, personally I somehow doubt that the amount of new customers will get reached (at least in 2016). Moreover, I also think that in 2017, but certainly in 2018, FP2 will increasingly be considered as an old phone (from the hardware specs), and that the amount of new customers might decrease steadily.
The subscription model here assumes approximately a two year usage, which I guess sounds reasonable, but could also be calculated for a bit longer period (maybe 2,5 years on average, or even 3?), I guess. For me personally I might prefer a subscription model, because I am not convinced if I would stay with an OS over several years (would be a novelty for me ;-)), as I might also try another one (if another one gets released). But I could imagine, on the other hand, that for other customers the subscription model might still be more interesting than a one time purchase, and sticking longer to SF than for 2 years. However, the poll suggests that users tend to prefer a one time purchase.
Of course it will be interesting to see how many FP2s will have been sold by the end of the year, but considering that FP was calculating to sell 140k phones per year, I have the feeling that also this target seems a bit ambitious, and then it would still mean - according to the calculations above - that almost a third of these devices should run on SF.
Maybe the interesting questions will be, how many new customers will get attracted to the FP2 through the mere fact that SF will be available. I have no clue about how big the community of SF is, or how big the interest in SF could be, but this of course might render my thoughts above obsolete. If indeed there is the belief that these numbers could be reached on top of the 140k, than I am much more optimistic to see the numbers from the calculations feasible, as I could imagine that 10-20% of the “regular” FP2 customers might be interested in switching to SF as well.
Of course everything I said above is based on my own assumptions and on my opinion, I have no evidence to back that up
In any case. I would be very happy to see an official build of SF (soon) available for FP2