Here’s a great way to waste money. Avoid thinking about how much something really costs. It’s surprisingly easy to manipulate prices in such a way that they seem cheap when they’re not. Being able to see those manipulations will help you keep your spending in check.

Here are the top five things you can do to avoid getting gently scammed.

First, beware the “false option”. Have you ever looked at a website selling (whatever) and noticed that there are three similar versions of the same product or service, with one of them being “high-quality” but ridiculously expensive? And you think to yourself, “Wow, who are the chumps who buy that insanely high-priced third option? I don’t need to be wasteful. But I don’t want to buy poor quality either. I’ll buy the middle option, reasonably priced.”

See, they got you. Here’s how.

That ridiculously priced third option? No one buys it. It’s just there to make you think the kinda-overpriced second option is reasonable. It anchors your expectations and makes you think you really got a deal but didn’t.

Remember: the real price of anything is just its price. It doesn’t matter how its price relates to some other price!

Second, beware of recurring monthly charges (like gym memberships). Always look to see if they have cancellation fees, and check to see for how long you have really promised to subscribe. Are there hidden non-refundable fees?

And of course, ask yourself how much you’re paying per year, not just per month. 30 dollars a month sounds cheap, right? But what about 360 dollars per year? Is that still cheap? How about 400 dollars a year, once you’ve added in all the hidden fees?

And not to mention, you can forget that you’ve subscribed and end up paying hundreds of dollars if you are not in the habit of checking your bank statements regularly. This very month I ended a 200 dollar per year subscription that I forgot was automatically renewing. Fortunately, it was also the sort of subscription that you can cancel with a refund. But please don’t rely on such luck! Subscriptions can get you because there is always that possibility that, once you’ve signed up, you will forget to unsubscribe.

Third, if you pay with a credit card, how much will it really cost once you’ve paid all the interest associated with the purchase? Turn those percentages into real numbers. You might be surprised at how fast they balloon out.

The problem with credit card debt is that it’s so easy. But you can change that. Make credit card debt hard by forcing yourself to do the math. Really sit down and figure out: if it takes me two years to pay off this purchase, how much will it really cost?

Fourth, what else will you need to buy to make it work (whatever it is)? It seems like every time I try to purchase software or technology it sounds like a fantastic deal at first. Then things start to add up. “Oh, you have to buy this doohickey here and that little tweeter over there.” Suddenly there are service charges and other random fees.

The most obvious version of this borderline scam is printers. You can buy these printers for practically nothing, but then the ink cartridges are prohibitively expensive. It’s the same with cheap weed-whackers. They get you when you need to purchase more line (and beware of weed-whackers that automatically feed more line as you go! You should already know where the company is making its real money.)

Remember, you can say no at any time. You can say no half-way through the purchase process. There’s no sense in continuing to make a mistake just because you got a good start on it.

Finally, here’s the real trick. This might be more important than all the others combined.

Do you get paid by the hour? Look at what you are considering buying. How much does in cost in hours worked? Think in hours, not dollars. When you think, not about money, but about how much you had to work to buy whatever it is you’re considering, is it worth it? Ask yourself that question every single time you want to buy something, and your attitude towards spending money will start to change.