If you want reasonably priced suits "off the peg" i suggest Pierre Cardin in city centre mall. They have Pierre Cardin, Dunhill, Daniel Hector etc etc. I think the stuff is stitched in Syria but its not fake and well made. They will also alter the suit to your requirements. They always have 75% off!!
Expect to pay
Silk Tie 30-50
why would u say tht "Designer" is a good tailor.
If you want suits, the best thing to do is wait for Blue Salon or Modern Home to go on sale...you pick up Italian suits for cheaper than almost any where else in the world (I've priced it...)
On sale, expect to pay QR1500 to QR35000 for Aramani, Valentino, Zegna and Moschino suits.
(no idea about the tailor though! if you find a good one be sure to tell the rest of us)