The wealth of France in 1871 was estimated at a little less than half that of Germany in 1913.

Apart from changes in the value of money, an indemnity from Germany of $2,500,000,000 would, therefore, be about comparable to the sum paid by France in 1871; and as the real burden of an indemnity increases more than in proportion to its amount, the payment of $10,000,000,000 by Germany would have far severer consequences than the $1,000,000,000 paid by France in 1871.
There is only one head under which I see a possibility of adding to the figure reached on the line of argument adopted above; that is, if German labor is actually transported to the devastated areas and there engaged in the work of reconstruction.

I have heard that a limited scheme of this kind is actually in view.

The additional contribution thus obtainable depends on the number of laborers which the German Government could contrive to maintain in this way and also on the number which, over a period of years, the Belgian and French inhabitants would tolerate in their midst.

In any case, it would seem very difficult to employ on the actual work of reconstruction, even over a number of years, imported labor having a net present value exceeding (say) $1,250,000,000; and even this would not prove in practice a net addition to the annual contributions obtainable in other ways.
A capacity of $40,000,000,000 or even of $25,000,000,000 is, therefore, not within the limits of reasonable possibility.