We did a 100 point add on at VWL while on the Disney Magic way back in 10/01. At that time we owned 200 points at BWV (originally bought 170 points, then did a 30 point add on). So now we have 100 at VWL and 200 at BWV, and this is just perfect for us.
As far as special offers - the going rate at the time was $75 a point. If you "sold back" the first year's points, you got $10 off per point. So we technically "paid" $65 a point. We had to put $500 down and financed the other $6000 (which I'm happy to say we paid off in 3 years!). We also got a lovely scrapbook type photo album.
Sorry, I can't help with what current special offers might be.