While FastFlight brand material is more, B50 is about $8, FF about $24 per 1/4# spool, it's also twice as much material. B50 is 4200' while FF 8900' (per pound I think). So if a B50 string costs 30 cents, a FastFlight string costs about what... 45 cents? But you have to be able to afford the up front cost to buy into a whole 1/4# spool, although I think it's available in smaller quantities.
I posted to say there is no standard for selfbows or wooden bows, especially not B50. It is inferior in performance to what was the standard for millenia, linen, but does not wear out as quickly. Absolutely no advantage can be had shooting B50 over FastFlight, where resistance to wear exceeds B50, and tremendous benefit in terms of handshock and cast can be had by shooting FF.
For the life of me I cannot comprehend the entrenchment wrt to use of B50, especially in the selfbow game where you would think foks were more open to new ideas, more adventurous in their choices, more objective and thorough in their assessment of performance.