At the risk of repeating myself, Lignum vitae would be a fantastic wood for a shadow pattern handle. I don't know if it's too expensive for the price point, but functionally speaking it's hard to beat.
See what I did there?
Edit to say: I find Bocote somewhat ubiquitous these days. It is a fine wood though.
My vote on Lignum Vitae as well. Aside from the historical significance (being used as bearings, even before babbit), and it's unique properties in the wood world (so dense it won't float) - it's some pretty awesome stuff. Lots of color variation (streaked with greens to browns), VERY stable (not likely to crack, warp or check - or lift away from the liners), and a chatoyance not found in many woods. It has a peppery-menthol like smell too, very fragrant.
I only have 1 knife with lignum scales, but it's a modern OHO - carried a lot, but looks as good as new many years later.
Regarding price, we're talking about tiny little chunks to make scales from - it's not going to add that much, certainly no more than any other exotic (wood, bone, stag, etc...).
Edited to add: A few other notes about wood. Personal experiences only (I'm a hobbyist wood worker), YMMV....
Osage Orange (Hedge Apple 'round these parts) is beautiful wood. I have a particular fondness for it, especially for making mallets, axe handles and fence posts. However, it SUCKS for knife handles. It's porous, stains easily, only looks pretty when new, and is actually very toxic.
Purple heart only looks purple when freshly cut - it turns poo-brown when exposed to UV light and oxygen. It's VERY brittle and splinters easily. It would be very difficult to pin scales on without cracking, and a bare head design would be next to impossible.
Others, like maple, bocote, zebrawood, padauk, etc... are actually very soft and won't hold up to long term use very well. Cocobolo, being a nice oily rosewood, makes great knife handles - although it's very brittle as well. I don't think it would tolerate the stress of a bare head. Ebony is cool, the black & white stuff would have a unique look, but we've kind of been-there-done-that with plain ebony already.
Lignum Vitae addresses all of those issues, and would likely be one of the most durable (and, dare I say - most attractive

) knife handles ever produced. Also, I just looked at a few lumber sources - it would cost approximately $2.50 per knife for the material. Seems reasonable (and a lot cheaper than micarta).
It would be interesting to hear the knife manufacturers perspective on woods - I'm not sure how they look at it, although they all seem to offer a fairly wide variety.