Major deals await shoppers on Black Friday and Cyber Monday, but sometimes sales aren’t always what they seem. One tried-and-true retailer trick is to mark up products before a sale, then reduce the price so it seems like you’re getting more value than you really are. According to Fast Company, this has been a source of complaint for Amazon shoppers who claim to have noticed the trend on third-party Amazon listings. That 65-inch LED television for just $1500 sounds good, until you realize it's always been $1500—a seller may have simply marked it up to $2500 just before the sale.

So how can you tell when you’re getting a deal? One solution is a price-tracking tool. These apps and browser extensions essentially act as a personal shopping aide, monitoring Amazon for price fluctuations. If a product goes on sale, you’re able to see what it typically sells for—and in some cases even anticipate what it might sell for down the line given its pattern of discounts.

One such extension, Keepa, will assess pricing on specific products and then send you an email alert when it drops below a set amount. A pricing graph can tell you whether the savings are really worth it; Keepa also factors in Prime Exclusive offers as well as coupon deals. You can even import your Amazon Wish List products.

CamelCamelCamel is another price-tracking tool similar to Keepa, though this one requires you to open a (free) account in order to use it.

Price trackers also act as a de facto discount tool. By keeping a product you’ve purchased on the extension, you’ll be alerted to any additional price drops.

But be advised that knowing about a lowered price doesn’t necessarily mean you’ll get it. Amazon doesn’t have a formal price adjustment policy, so while you may have luck contacting customer service to get a partial refund, you may also have to resort to returning and then re-purchasing the item. Whether that’s worth the cost savings is up to you.

This article was originally published on www.mentalfloss.com as How to Know If You’re Getting the Best Possible Price on Amazon.