Woodywoodwood: You might be right, but I'd love to see the contract between Kingfisher and DeWalt, if that's the case. It would make fascinating reading, and introduce nightmarish post-sales issues: "But it's your tool, you made it! Why won't you honour the warranty???" Etc., etc.
In my limited experience in manufacturing, we tried as much as possible to minimise the variants we sold branded (OEM--stuff we made with other people's names on it--was a different kettle of angry lobsters tho.). The more unique elements there are, the more expensive a product becomes to make and support post-sale.
And there are hidden costs too, for example the cost of actually saying "No. We didn't sell it with a warranty, so we won't repair it for free." That's inevitably bad publicity, and by word-of-mouth and/or the internet (the worst sort really). And you've still had the contact cost - bloke at service desk or a parcel arriving, or whatever, which costs resources just to say "no" to*. All it ultimately does is damage the brand, and any additional profit per unit, either from cost savings in manufacturing or lower cost of sales quickly evaporate. There would have to be a really, really good reason for DW to do that, and I can't see one (on the face of it).
There might be more truth to the Wurth-Bosch thing, as I can see sound commercial reasons there. In volume manufacturing you need to be able to ramp up production as fast as possible, as production processes stabilise (and quality improves). So there's an argument that some components might benefit from going into as many outlets (products) as possible, as that makes the unit cost lower, and probably improves the yield and reduces the failure rate (after they're sold). In the context, I'd guess at things like gearbox components, electronic speed control, wound motor components, switchery, turned shafts, etc. And the plastic moulds don't care much what colour plastic squirts into them.
And IIRC, there are only a couple of plants worldwide that make those 10.8V batteries: the outer shell clips on so they can't be interchanged between different brands when they're sold. That said, power cells are one of the few areas where they're tested after manufacture and quality-graded - the "failures" are sold off as cheaper brands.
E.
*Another thought occurs to me: Festo/Festool are nothing if not very clever people. It may well be that their model - build excellent after-sales support into the price - actually means they have lower per-unit support costs than cheaper brands with poorer reliability. The item itself probably doesn't cost much more to make to a higher quality, but the service interaction builds the brand rather than leads to customer frustration (generally!), and they see fewer back anyway (so the per-unit support cost is lower).
