I was at Costco picking up some stuff and saw a 14 pack of disposable Mach 3 razors for $25, and with the $5 coupon, becomes $20 for 14 sets of blades. Turns out the catridges do separate from the handle and fit in standard Mach 3 (Mach 3, Mach 3 Turbo) handles. For comparison, a 12 pack of cartridges at CVS are selling for just over $20.
Now all I need is to figure out what to do with 14 handles!