Just got back fm Dahab where I bought my fins, and my travel buddy his 7mm suit, so have just the right info for you!
Would recommend to buy your gear in Dahab, Sharm is about 15-20% more expensive and I don't know if you can bargain your way down in Sharm.
Cressi 7mm was bought at Scuba One, located next to the taxi stand Masbat. Price paid: 1.250 pounds. That's a good deal, locals/Divemasters do get a bit more discount, but not much.
Fins Tusa Imprex bought in other shop: walk fm taxi stand Masbat in direction of Lighthouse area, pass the entrance of Nesima, on your hand it is the shop just before the bank/ATM. Bought for 280 pounds and booties for 150p.
Have FUN, beautiful water out there :-)
Charlotte