Governments around the world have the same measure near the top of their agenda: increase the Gross Domestic Product (GDP). Sure, some governments have a housing crisis to deal with, other governments care more about agricultural policy, but GDP is the most prevalent.
A quick refresher: GDP is the value of all goods and services exchanged. You can estimate it by adding up all production, all income, or all expenditure in a country.
What makes GDP a good measure? Because it is a credibly neutral way to express progress of many other values. GDP measures the rate at which money changes hands voluntarily, which makes it a decentralized indicator of how much people are getting what they want. GDP encapsulates all other values in a neutral way.
A common complaint is that people who want to optimize GDP will miss out on e.g. environmental care. This is not entirely fair, because if people value the environment, the exchange of goods and services which benefit the environment will cause GDP to go up. Indeed, even government expenditures cause GDP to go up.
A more fundamental complaint is that GDP does not measure all valuable activity.  To give one big example: legislative changes have an enormous impact on society, but it is unclear for both legislators and citizens how much value certain adjustments cost or contribute. A way to overcome this is to allow people to indiciate their willingness-to-pay for certain legislative changes. In more common language: it is time to measure the value of votes.
Measuring the value of votes
We typically can't estimate the relative value of a vote. How many bananas would you offer in exchange for voting in a presidential election? And how important is a regional election to you compared to a shareholder election of your company? Imagine a government stimulus program which attempts to increase the amount of voting, how much subsidy should your local football club get to hold monthly elections? These are questions which are currently very difficult or even impossible to answer.
Proposals to make the value of votes measurable don't have to be limited to a particular organization or voting method. Voting in both public and private organizations could contribute to GDP, whether they are cast using First-Past-The-Post, Approval voting or Ranked Choice Voting. Measurable votes still leave the door open for stimulating a great diversity of voting experiments.
The value of votes could be determined in the same way that the value of any other product is determined: put the votes up for sale on the open markets!
By allowing people to buy votes, you can directly measure how much the votes are valued. The most common concern against vote-buying is that it goes against the value of equality. The poor can afford less votes than the rich. If votes could be bought, society could degrade into a plutocracy, run by the wealthy. While it is an important concern, it is not strong enough to discard vote buying entirely. In fact, vote-buying is already wide-spead in the private sector: you can purchase shares with voting rights of any public company right now! Balancing economic efficiency and equality is not just a political question but also a science.
Equality can still be promoted by:
- Giving everyone at least one vote
- Making votes more expensive the more you buy. In the seminal paper Quadratic Voting: How Mechanism Design Can Radicalize Democracy, Lalley and Weyl argue that buying votes with a quadratic cost can be optimal. See an extensive exploration here.
- Another possibility would be to scale the cost of votes by people's wealth or income, essentially using price discrimination. Here is a proposal applying price discrimination to any purchases; Posner and Weyl (2017) also propose it. Large challenges remain to make this work, as wealth- and income-tax evasion and avoidance are widespread. It is still too easy for powerful people to hide how much power they have.
The above proposal all require that votes are tied to an identity. Selling your votes to another person would therefore not be allowed in any of these schemes. Though a particular vote might be accepted in different places, votes will never be as fungible as money.
This scheme does not require more government surveillance than we already do. We can measure GDP even though the government doesn't have a total view on each individual transaction. You just have to add up e.g. everyone's income. Any public or private institution which wants to mint additional votes could do so, and they can even earn an income in the process. Votes just become another good on your shopping list. Additional value is created both because people can express different levels of interest and expertise:
"Moreover, QV, unlike 1p1v, allows not just for the expression of different degrees of interest but also different degrees of expertise and knowledge about issues. One might therefore expect it to perform better than 1p1v in such common interest settings when degrees of expertise differ across individuals and issues." - source
Vote buying in practice
There is a long road ahead to make vote buying a reality. There is promise, but a broad multi-disciplinary view is needed to bring it to fruitition:
"Perhaps the most important takeaway from the Kaplow and Kominers analysis is that the real-world performance of QV likely will depend very heavily not merely on economic or even psychological factors, but on the sociology and political organizations that form around it" - source
 Money is a tool which is used to coordinate large groups. It should therefore not be a suprise that GDP measures exclude valuable activity happening within families and small groups. All of the free childcare which parents give on a daily basis are of tremendous value, but they don't contribute to GDP. As the saying goes: "the best things in life come for free", and it is unclear whether we'll ever be able to or want to measure the value of activities happening at a small scale.