Depends on the type of cue and condition of the cue, depends on the clarity/condition of the signature, depends on the reputation of the company that issued the COA.
If it is just a no name, good condition SP, with a pretty decent signature, and a good COA, yeah, I'd sat it's wortha few hundo. He signed many things, balls, books, etc, but not many cues, and that makes it a little cooler in my book...
I'd say the best way to find out is to post a picture, with the COA, and put in the For Sale section with a BEST OFFER, and that will tell you exactly what it is worth, what somebody is willing to pay. I'd love to have something like that....