But compare this to transgender peoples, who are marginalized, disproportionately homeless, almost universally imprisoned, and make up a very disproportionate percentage of the lower class (usually they 'fall' to this class rather than being 'borne of it'). It is unlikely that transgender people could buy the votes to achieve policy measures they felt necessary just as it would have been impossible for slaves and poor indentured whites and immigrants in the 1700s and 1800s, Native Americans pushed from their land and made to walk trails of tears, children working in factories, or women for these same centuries (who in addition to having effectively no political voice also had few reasonable financial options) to 'buy' freedom.
Additionally, entrenched interests within classes - and in disputes between them - make it easy for the upper division of the wealth distribution to buy political power to block the opposing classes vote, this exacerbated by high wealth inequality. That is to say so-called Quadratic Voting also depends on the wealthier class having no strong opinion - yet its very easy to find examples both today and historically where this is easily shown not to be the case.
So its suspect whether today's working poor, child laborers, blacks and latinos, immigrants, or members of small (or no) unions would benefit from a system like this.
Finally, these market based solutions to voting would be yet another way to trade financial power for political power. The history of all governments show how strongly political power already responds to wealth. Is it smart (and ethical) to make votes market commodities?