No it's not a conversation starter unless you enjoy conversing with a donkey. The question is akin to "How much is it worth?" It's an obnoxious question that seems kosher only to those with no tact or manners. It doesn't upset me after I answer it's not for sale...any further statement to the matter is rude and unwanted.
Other questions along the same train:
Your wife is pretty...what is her bra size?
That your daughter?...she 18 yet?
Nice car...what's the retail on one of those?