I'm not trying to argue you into a sale from Monaghan Consultants Ltd, the slim profit on each sale would not be worth the effort
The problem with going by your own definitions is when things go wrong. Using your examples, if you have an accident in your car and you have business samples in it your insurance company may well class your use as business use, should you have not declared this, then they have every right to not pay as the car was being used for a purpose it was not covered for. Storing samples in your house may invalidate your house insurance in the same way.
My observation was not aimed specifically at you, but at the fact that many people conduct business without the required tools even when they can pay for these tools and deduct the cost from their tax bill (in effect keeping the bottom line profit the same as cutting corners).