They are actually almost 3 lbs lighter than stock, I weighed my stockers at 21.3 lbs each; I dunno where the 19.5 lb myth started. Either way, 21.5 is still plenty light for a stock wheel.
Besides - that 17.8 lbs is for an 18, not a 17! The 17's are 16.8 lbs FTW - FINALLY a lightweight wheel! I will haz a set teh soon, too bad I have $$ going to other things at the moment or I'd buy them NOW.