In reply to l'amour:
Tulipwood is one of the least expensive hardwoods and machines well, I'd imagine that's why beastmaker use it. A fingerboard doesn't have any fine detail so I think you'd get away with most hardwoods if you want to use a solid block.
I made a board a while back out of plywood. I cut 10 copies of the board shape out of 5mm ply and then cut the slots out of each sheet. So for the 10mm edge I cut a slot in the first two sheets, for 20mm the first 4 etc. I then glued and pinned all 10 boards together. It worked well and was cheaper than buying a solid block of wood.