Never, cause I don't ever own an expensive chalk
Why would I buy an expensive chalk when the best chalk in the world costs $2 for a whole 12 chalk box! Thats right, 1 dozen of chalks I bought them for $1.99 from seyberts. Sadly these chalks are removed from seyberts I think.
They are called Silver Cup and theyre truly amazing chalk, Seyberts had them on sale I think so i snatched a couple of dozen boxes, i bought blues and white chalks and surprisinglly to me the white chalks are actually fantastic which I didn't thought they will be....they dont leave much coloration into your hands at all, plus they do minimal dirts on the felt (less than blue chalks).
Not to mention also this cheap chalk is actually really good because when I used them I noticed that there are far less skid's as opposed as when I use those premium fancy expensive chalks.