Assuming your uncle was single and not able to leverage the double estate tax exemption for married couples, the $1,000,000 farm value is only $11.92 million short of the threshold at which estate tax would start to apply, and only to the amount above the threshold, at an initial marginal rate of 18%. It only reaches a marginal rate of 40% on the amount more than $1 million over the exemption threshold.
If, instead of being $1 million, the farm (assuming it was the whole of the estate) was worth $13.92 million, the actual estate tax would be $345,800. Assuming the same ratio of annual profit to value in your hypothetical, the annual profit would be $278,400; so if you had no other assets to pay the tax, you’d probably need to borrow against the profits, but that shouldn’t be too hard given their magnitude.
If, instead of being $1 million, the farm (assuming it was the whole of the estate) was worth $13.92 million, the actual estate tax would be $345,800. Assuming the same ratio of annual profit to value in your hypothetical, the annual profit would be $278,400; so if you had no other assets to pay the tax, you’d probably need to borrow against the profits, but that shouldn’t be too hard given their magnitude.