I'm not sure, but I wouldn't be taking it as salary. Company buys coffee machine at a cost of €875 net of tax and anything left goes to corporate investment account within the company.
If you're just trying to maximise the value of the company, then the rational course is not to buy a coffee machine at all. That maximises the company's retained profits and so the balance in the corporate investment account, and you can just as easily use the existing machine in the kitchen at home. So the whole buy-a-coffee-machine thing makes no sense unless the object is to benefit you, not the company. And therefore we should compare the alternative methods in terms of the value they each confer
on you.
What's the worth
to you of an extra $1125 in the corporate investment account within the company? The funds are going to come out some day; otherwise they're no use to you. Which means that, if what we're trying to compare is the value to you of the alternative methods of buying the coffee machine, we have to factor in the cost of taking the money out of the company under both options.
One thing that emerges from this is that the amount of the tax deduction is a bit of a red herring. Even if there were no tax deduction at all, you are still €500 better off if the company buys the coffee machine and pays you €1,000 than if it pays you €2,000 and you buy the machine.
One factor that we haven't included is that, if the company pays you and you buy the machine, you own the machine and, when you no longer require it, you can sell it. If the company buys the machine, the residual value accrues to the company. But I'm assuming that the residual value of an 8-year old coffee machine is nil, or as near as makes no difference.