There are 58 million Netflix subscribers in the United States and 137 million worldwide. Odds are that you’re one of them, so we have a quick question for you: How much do you pay for the streaming service per month? You need a minute, don’t you? You’re not the only one.A new report from the consulting firm Waterstone Management Group found that many people have no clue what they shell out for subscriptions services like Netflix. Even worse, of those who took a guess at what their monthly subscription costs were, a whopping 84 percent underestimated. For the study, Waterstone asked 2,500 adult Americans to think about the many subscription services they used. The researchers then asked participants to estimate how much they spent each month on those products. The participants were at first given 10 seconds to reply. The researchers then prompted the participants with specifics, like Netflix, and gave them 30 seconds for another guess. The average first guess on monthly subscription costs was $79.74. The average second guess jumped by 40 percent, to $111.61 per month. Both guesses were way too low. The Waterstone report found that the average American spends about $237 per month on subscriptions (which included phone service and wi-fi).The problem here is obvious: People are shelling out a lot of cash for subscriptions and they don’t even know it. This means it’s time for a cleansing. Go over all your monthly subscriptions. If you haven’t used one (or have been unsatisfied by one) in two months, cut it. There’s a good chance you’ll end up cancelling a few services and saving some cash in the process.