hi my audi s4 starter motor has come to a end, would like to no the cost to replace it 

Hello Ryan,

Many thanks for being in touch with the forum. 
Labour costs will vary from region to region, and obviously whether you propose to get this done at a main dealer, independent, or your local garage. I guess you won’t be considering a main dealer for a car of this age, but they will obviously be able to give you a cost which can be used for comparison, so it worth you just ringing /calling  in at the other two alternatives, to obtain a costing in your area. 
Quality of parts? Cheap is usually just that, and although you might get a 1 year warranty, you will still have to meet the labour costs. Personally, I would not buy an electrical item on a cost-is-king basis, but you will need to make your own decision on this.

Kind regards,

Gareth.

p.s. Are you sure it is the starter which is at fault, rather than electrical connections/ earths / battery?