Worst case...OEM piston/cylinder=$250, crankshaft assembly $257, carburetor $100. Should be able to get a shop to put it together for $300-400. So $800 wouldn't be crazy.
Now, if the saw has little use and just fried a piston and jug can be saved, oem piston is about $100. If carb kit is all that the carb needs, you're looking at $10.
If the piston is simply worn down from high hours of hard use but jug is still okay, it might be a bad idea to skip changing crank...it's all how much you want to risk. If you're paying someone else for labor, the risk is greater (i.e. you spend $500 on new top end, crank goes and ruins jug..now it's replace everything time)
If you plan to throw an aftermarket piston in for $30 and call it good on top, then of course you won't replace a crank that seems okay.
In summary, "re-done" can mean somewhere between $30 and self supplied labor and $1000 at a shop...
So, it depends.
