In the sandbox we exactly this

Stumbling and Mumbling:
In the Wheatsheaf last night, I was struck by an obvious injustice. The pub was charging everybody the same price for beer, regardless of their income. This is obviously unfair: why should the millionaire picking up his children from the posh school pay the same as a low-wage worker? Beer prices must be means-tested, so the rich pay more.
Astute readers might spot a problem with that paragraph. It’s bollocks. It would be grotesquely inefficient for barkeeps to check everybody’s income before serving their Tiger*. A far easier way of addressing this unfairness – if such it be – would be to tax the millionaire and give income support to the poorer customer. This would have the same effect as means-testing – the millionaire would be less able to buy beer and the poor person more able – but would be more efficient.

Beer drinkers tap the beer club icon and agree to take the regular rounds, under contract.  Then we can do it by inventory volatility, reduced, and the reduction is due to limited income purchasers banding together in a buyers club.