Ignoring that several parts are printed and you'll have to substitute blank versions; technically possible but would be much more expensive and time intensive than just buying the set. First off, it's quite unlikely you'll be getting everything from just one or two stores on bricklink, and local ones at that, so one of your major cash sinks will be shipping for each lot of bricks. After that there's any uncommon pieces which may go for $0.25-0.50 each and may require buying from several different sellers due to low stock, I think some of the transparent orange pieces would be a good example. Then there's the time spent finding all the pieces, balancing buying enough from each store to meet their minimum(or maximum if you find some really exacting stores) order quantities while not overpaying on shipping, doing all that for MOC is one thing but to make a DIY KO of an official set is just silly. If you really have to save a buck then it's either the inevitable KO(which may not be exact depending on how they substitute parts they don't have moulds for or colours they use) or a sale if retailer stocks it(and doesn't exempt it from promotions like Myer loves to do).