Is BS jewelry worth investing in?
 

More directly: Does it go obsolete with Kunark and/or become much easier/cheaper to make?

I don't want to spend a ton of plat on it to potentially have it lose 90% of its value if Kunark comes out in a few months.

opinion: Blue Diamond Electrum Earrings > Black Sapphire if you're wearing them for the HP. Same goes with the Blue Diamond Gold Pendant over the Black Sapphire Platinum Necklace.

I do not agree that wearing direct +HP gear is worth losing the amount of resists 2x Blue Diamond Electrum Earrings + 1x Blue Diamond Gold pendant would give you.

Is a combined 125hp from BS ears/neck better than 23 fire, 28 disease, 23 cold, 12 magic, 28 poison from BD ears/neck?

It's almost infinitely better at levels 1-49 IMO. I've never seen the planes and probably never will at this rate.

that depends on your class and what you're doing. I have a full set of resist gear (both masks, pendant/tiara) but I don't wear it until i need it (raids, and even the only on specific mobs and perhaps even depending on the situation). The black saph set is fantastic on a shaman and tanks/hybrids considering the lack of pure +hp gear in classic.

The earrings will probably get replaced in kunark, though that also depends on the class. The necklace is still very viable and will persist to be a great piece thru kunark

HP Gear is incredible if not vital if you're really trying to level quickly 1-50, depending on your class.

BS' will begin to drop more frequently in Kunark though, so those items should go down in price somewhat (IIRC).

Right now BS only drop off planes and the named lizard in oot. Come kunark it drops off dungeon trash like Seb. Price will only drop.

prices may drop, but the need for use will still be there. I recall needing BS resist gear for end game velious raids (dragon killing needs lots of resists)

black sapphires do not provide resists, you're thinking blue diamonds.

the velium black saph neck is 65hp/mana

Let's address the core of the question....Kunark....well my good friend; I would guess you have at least one year before Kunark launches. So when considering your market; assume it's just old world - no kunark.

so i was... it's been about 8 years 8)