The deals – better than Black Friday’s, according to Amazon – sound enticing enough: A 40-inch TV for $115. Fifty percent off two select Nikon COOLPIX cameras. The list goes on. And all you have to do to take advantage is join Amazon Prime, which usually costs $99 but will be free for the first 30 days. So should you – or should you not – take advantage of these so-called Prime Day deals? 7/15 update: Amazon Prime Day deals worth checking out. Prime, which already has 41 million members in the U.S., according to Consumer Intelligence Research Partners, is a good deal for many of the people who use it. “Our data shows that on average, customers use about $99 worth of shipping, at Amazon’s cost,” says CIPR’s Joshua Lowitz. Not only would the same shipping cost considerably more without the volume discounts Amazon nets, but customers get other program perks like photo storage, music access and video streaming. Recently Consumer Reports compared Amazon Prime to Netflix (which costs $96 a year for a starter package) and summed up: “All things considered the two are pretty equal and cost about the same.” Amazon 'Prime Day' deal list teases released Yet there are three good reasons to be cautious about the Prime Day program and other mid-summer savings deals: S-A-L-E is a four-letter word. Research shows that for many people, sales are too difficult to resist. They light up our brains like Christmas trees and often cause us to buy things we neither need nor really want (especially in hindsight.) Return shipping is not generally free on Amazon – even with Prime membership. Your shipping cost is usually deducted from the amount of your refund, and those costs can add up quickly. So if you know you tend to pounce too quickly on good deals, steer clear not just of Amazon on Wednesday, but Walmart, which has jumped into the fray with a longer online sale, and Nordstrom, another Seattle-based retailer that’s holding its annual anniversary sale. Also, think twice before joining Prime with the intention of quitting later. Walmart announces big online sale to compete with Amazon's Prime Day Inertia is tough to fight. Do you know how many health clubs make their money? They sign people up in January and then wait for them to stop coming without canceling their memberships. This is the same strategy magazine publishers use to retain subscribers and “blank-of-the-month” clubs use to keep you in trial-sized cosmetics (Birchbox) or athletic wear (Kate Hudson’s new Fabletics line). If you don’t think you’ll remember to quit, don’t join in the first place. Also, membership in Prime may limit your inclination to shop around. For a while, big box retailers like Walmart and Target were petrified that customers would use their mobile phones to check Amazon prices while in their stores – a practice known as “showrooming,” says CIPR’s Michael Levin. Not so much anymore. Why? Because Prime customers “aren’t going to Walmart.com, they’re going straight to Amazon,” he says. CIPR’s research shows Amazon Prime customers spend about $1,100 a year on the site; non-Prime customers spend $700. Are they getting a good deal every time? Or has free shipping made them a little lazy to check elsewhere? At least sometimes, it’s going to be the latter.