Personal data obviously has great value, or else the US government, Facebook, and Google wouldn’t be collecting it. But just how valuable is it? A handful of companies are trying to answer that question—and promise to share some of that value with those whose data is tracked.

Already, companies such as Epsilon and Acxiom gather and sell data on consumers, but they don’t involve consumers at all. Their wares include email addresses, and information about customer interests and offline activities, according to a Federal Trade Commission report (pdf) in May. This information is collected without consumers’ knowledge and is mind-bogglingly comprehensive: One company’s database had information on 1.4 billion consumer transactions, as well as 700 billion other elements. That means companies can build a pretty detailed picture of your habits, and even infer sensitive information like whether you’re pregnant.

Some companies see an opportunity to enrich this gushing river of data by paying consumers directly for their information. One, Datacoup, ran a pilot program that paid users $8 a month for access to their social media accounts and a feed of credit card transactions. Another, Luth Research’s ZQ Intelligence, pays users $100 a month to be tracked on their devices and to answer questions about their behavior—essentially, a souped-up focus group.

They may well find takers. As it turns out, not everyone minds being tracked: A survey of 1,100 smartphone users in April found that almost a third of respondents would share their data if they got something in return.

The actual value of information gleaned this way varies widely, making pricing rather difficult to determine. Datacoup settled on the $8 figure to attract users, CEO Matt Hogan tells Quartz. Not every user’s data may be worth $8, but to gather a large enough pool of behavioral data to sell, the company will continue to pay up to $10 a month to those willing to be tracked, Hogan says.

The data’s value is also context-based, says Mike Rudoy, a co-founder of the startup Ridley.io, which also aims to cut users in on the sale of their data. Certain people are worth more to specific companies: Ford or Chevrolet, for example, will pay a premium to buy ads that will be placed in front of users who are about to buy a car. And a company specializing in women’s yoga pants will pay more for user data on women who do yoga.

The same FTC report called for the US Congress to enact new legislation so that consumers would know how their information is being used and stored. But as of right now, there’s no way to really know what’s being collected by data brokers. The promise of these startups is that at least under their system you’ll get a small cut of the value of your information, as it flows into that giant river of data.