Your brain plays many tricks on you when you’re shopping. One that I almost fell victim to when I was buying our newest (used) car was this one: As the amount of money you’re spending increases, you are less likely to save money in little ways.

In my case, I bought a $19,900 minivan. I had negotiated the price down from somewhere around $23,000. It was worth an hour of my time to do the bartering that resulted in paying $3,000 less. Heck, most of that hour was consumed by getting the price from $21,000 to $19,900. So, saving $1,100. An hour of my time is worth $1,100 after taxes, right?

So why, when the dealership offered me $400 if I traded in my $1,500 car, was I even considering the offer? It would be so convenient to just make the exchange right there. I wouldn’t have to buy a new license plate for the new (to us) minivan. I wouldn’t have the hassle of listing the car on craigslist, meeting buyers, etc.

But it was worth at least an hour of haggling to save $1,100 on the car price — why not sink a few hours into selling the car, to make $1,100 more than trading it in? This is due to our tendency to think in relative, and not absolute, terms, a recent New York Times article points out.

So, what should you do?

Trading in your car is super easy: Clean it out and hand over the keys. Your final invoice on your new-to-you car is reduced by the amount of the trade-in.

Selling your car is not as easy, but it’s not much more expensive to do so. Here’s what you need to do:

• Understand how much your car is worth, by looking it up on all three car valuation sites: Kelley Blue Book, Edmunds, and NADA.
• Buy your Carfax report (potential buyers will ask for it)
• Clean out your car, wash the exterior and interior
• Take photos and list on craigslist or other used car-buying sites
• Set up appointments with potential buyers and meet with them in a neutral, safe location
• Allow potential buyers to test drive the car
• Come to an agreement on price
• Drive the car to the buyers’ mechanic of choice (if the buyer wants; the buyer pays for the mechanical inspection)
• Fill out the appropriate DMV forms and take a cashier’s check or cash for the vehicle

How do you know if all of that effort (maybe 3-5 hours) and investment ($50-100) is worth it? Subtract the costs of selling it on your own from the purchase price. Then subtract the trade-in price offered. Divide the difference between the trade-in value and sale value (minus costs) by the number of hours you spent selling the car, and you have your hourly rate.