... £6k a year, that would cost something like £200,000 to purchase
The reason that isn't equivalent to wealth is that you're not "entitled" to it in any way under your control. There is no fund of equivalent value in which you have a share, all you have is a promise that a future government will require future taxpayers to pay you that sum out of their earnings.
If there's noone to tax (because the winners are offshore and the losers are impoverished), it will quickly become apparent that "wealth" is of very little value.