Collective suttee: is it unjust to develop life extension if it will not be possible to provide it to everyone?

If we can anticipate that life extension will be too expensive to provide to everyone, is that a reason not to research and develop it? Collective suttee is the policy of inhibiting or prohibiting life extension on such grounds: just as widows are killed on their husbands' funeral pyres, potential Methuselahs would not be allowed to outlive everyone else. However, in other contexts we judge that taking from the haves is unjustified when doing so confers a merely marginal benefit--or no benefit--to the have-nots. By this standard, collective suttee is probably unjustified, for the burdens borne by the have-nots are likely to be too small to justify denying extra decades or centuries to those who can afford it.