Naturally there's a much greater supply of flat-sawn stock than quarter-sawn. This fact, and the superior tonal and structural characteristics of the quarter-sawn stock, are manifested in the higher price. A lot of flat-sawn ebony is sold these days for tonewood purposes, and used for fingerboards. Its resistance to wear is just as good as that of the quarter-sawn type, but there's a higher risk of warping and shrinkage. (Ebony is sensitive to water anyway!)
In tonewoods generally straight grain is the most preferred from the structural point of view, but aesthetically figured rosewood can be very beautiful, so it's highly prized. Brasilian rosewood (BRW) is a kind of timber where the figured variety can be just as good, from the tonal point of view, as the straight-grained type. However, knots, curls, and other grain irregularities always bear a risk of becoming structurally unstable in time, especially if the storing conditions are adverse (sudden temperature and humidity changes, etc.).
Music to hear, why hear'st thou music sadly?
Sweets with sweets war not, joy delights in joy...
William Shakespeare, Sonnet 8