Amazon offers its Prime members the Fiskars 45mm Contour Rotary Cutter, model no. 9521, for $7.56 with free shipping. (Non-members can spend $25 to qualify for free shipping; otherwise, it adds $5.18.) That's the lowest total price we could find by $9. Sales tax is added where applicable. It cuts multiple layers of fabric and paper, and features a retractable blade and curved handle.
Update: Note that this item is temporarily out of stock, but can still be ordered at this price for delivery when available.