patchouli is one of my most popular scents in soap. while i don't care for it myself alot of people do, it reminds me of a dark musty basement.
i also offer a sandalwood patch and this one i can handle.
as far as the discoloration it depends on the type of patch. the older it is the better it is and the darker it will get.
yep it's a little pricey right now. i had like 3 lbs of it stashed away so i should be good for awhile i am hoarding it and being picky about using it in blends.
solas has a patchouli fragrance oil that is reasonable and while not as strong as the real thing i have used it in a couple of blends with some fruity fragrances and it wasn't too bad.