it does at the high end of the scale, use a nymphs cloak and blade of roses for a sizable discount (at least if your cha was 18 to start with).
on the other hand, there´s a ring of human influence that turns it to 18 anyway so if you don´t mind being an ugly, smelly, antisocial slob of a powergamer, reduce it to 3 ;)

I can confirm that CHA *DOES* affect prices but only with high values. Send your PC in to see Ribald with a 14 CHA, and then boost the CHA using any of the following items:

Ring of Human INF: Base set to 18
Cloak of Nymph: +2
Blade of Roses: +2
Helm of Glory: +1
Plate of Balduran: +1
Axe of Hrothgar: +1
Sensate Amulet: +2

Note that a CHA above 20 will not affect item cost IIRC, but let me demonstrate how much cash a high CHA can save at the start of the game:
Taking a fairly expensive item: The Staff of Ryhnn +4
Cost with:
CHA 14 Rep 12 = 22275
CHA 18 Rep 12 = 18900
CHA 20 Rep 12 = 16605
CHA 14 Rep 20 = 15525
CHA 20 Rep 20 = 9990

So with a rep that does not affect cost, but high CHA, you are saving 5670 GP = 25%. With a max rep and low CHA, the saving is 6750 GP = 30% (not sure why it is stated as 50% in the manual), but with max Rep and CHA, you save 12285 GP = %55, so you are always getting the 25% discount for the high CHA.

Strength also increases your chance of succesfully bashing open a lock.

Consitution's above 20 should give your PC immunity to disease according to PnP, but I don't think it's the case in BGII, but higher CON values do increase your natural regeneration rate (especially noticable when resting) a little ingenius idea Dundee had was to draw upon holy might *before* you rest, and as spells are active until the 8-hour resting period is over, you get 8 hours of natural regeneration with the high CON bonus!

Wisdom does give bonus cumulative priest spells also.

Phew!