I personally see inheritance tax itself being a deeply immoral construct, your estate was made out of money that was already taxed multiple times by multiple different types of taxes, instead of you being able to pass your hard earned wealth to your heirs, the state takes it away. If you owned a house your children might be forced to sell it because the tax on it could be 40%, if you got as mortgage in your early 30s, you probably paid it off in your early 70s which is close to the life expectancy of 78 if you are a man, so technically, you didn't really own anything and you were just a slave to the state.
Answer: it is worth the £3 mm only because land prices have been inflated by people purchasing land for tax planning purposes. Regardless of the rights and wrongs of the governent’s solution, the market has been distorted by an anomaly in the tax system.
Where x is anything other than a token amount it's basically impossible to generate x% of the land value at transfer in excess of all other costs such as wages, equipment, a reasonable salary for the family and any workers etc.
There's an argument to be had that land redistribution is something we want, but the Government really isn't being honest about that being what they are intentionally pursuing.