I spend most of my time writing about the health care system. But every now and again, I actually use the system, too. This past week, those two activities collided on a very specific subject: shopping for better medical prices, and why patients don't do it.

I recently decided to select a medical service strictly on price. This is something many economists think ought to happen more, to lower health spending. I was ready to do my part. Most patients, though, don't do this, even when they have to spend way more out of pocket to get the more expensive care.

In retrospect, I wish I hadn't either. The lower-cost procedure — in this case, an MRI — did indeed save my insurance plan money. But it created a worse medical experience for me, and was helpful in highlighting the trade-offs that patients must make in the shopping experience.

I wanted to help America by choosing a cheaper MRI

This past June, I stress-fractured my left foot. Though I spent six weeks in a very stylish walking cast over the summer, the injury has stubbornly refused to heal. Earlier this fall I saw an orthopedic specialist, who recommended an MRI to get a better sense of what exactly was wrong. He referred me to a large academic medical center for the scan, and I made an appointment.

My insurance quickly intervened — and, as a health care wonk, I was very excited!

I got a phone call one evening from a woman who asked if I'd consider switching to a private imaging center nearby that charged about $400 for an MRI — about half as much as the academic center cost. She offered to help me make the appointment, right then and there.

For me, the cost would be exactly the same; I'd have a $50 copay for the procedure regardless of where I got my foot scanned. But I'd long understood MRIs as a commodity health care service, essentially an advanced photograph that would come out the same regardless of who snapped it. So, in the sake of doing my part to lower national health spending, I switched to the cheaper center. I did so, as you can see in the below tweet, quite enthusiastically.

1st for me: my insurer saw I scheduled an MRI and called with list of nearby/cheaper spots asking if I’d switch. I did. Cutting costs, woo! — Sarah Kliff (@sarahkliff) September 28, 2015

The MRI went fine; the facility even let me pick out my favorite classic '90s CD to listen to during the procedure (if you're curious, I chose Alanis Morissette's Jagged Little Pill.)

My experience since then, however, hasn't been as smooth

To preface: I understand my list of complaints is relative minor and at the end of the day probably won't affect the ultimate outcome of my care. At the same time, I didn't think I was making any trade-off when I chose a cheaper MRI. Now I know that isn't true.

The first issue arose when I went back to the orthopedic specialist.

He wasn't familiar with the place my insurer sent me, and the imaging center had forgotten to fax him a copy of my test. This meant a half-hour wait for me in his office, and more work for the office administrators to track down the images and radiological report. My orthopedist works with a handful of imaging centers in the Washington area. This is typical of medicine; there are often close-knit groups of doctors who, for better or worse, refer among each other. (Sandeep Jauhar does a great job of explaining how this happens in his recent book Doctored.)

Getting an MRI at the expensive medical center would have meant a smoother experience. The administrators there would know the exact drill of how and when to ship off my scan. Instead, I inadvertently created a new inefficiency in my own attempt to reduce wasteful spending.

The quality of the image really was worse

Then there was the image itself. It did show a stress fracture that hadn't healed, but it was blurry and a little harder for the doctor to make out what exactly was going on. The academic center he refers patients to, he told me, typically sends back much clearer images.

I had actually expected this, thanks to a conversation I had this weekend with a radiologist who's engaged to one of my good friends. I told him excitedly about my cost shopping experiment (because I am, obviously, a very fun person to hang out with at parties). He was skeptical and mentioned how bad some of the images he looks at are. It's just like cameras, he said: Some people have expensive DSLRs, and others are working with a point-and-shoot.

During my wait in the doctor's office, I tried to search for evidence on disparities on quality in MRI images. I couldn't find much (if there are studies I missed, please email me). I did come across a blog post on the well-trafficked KevinMD blog from a neurologist making a similar point: There are good MRIs and bad MRIs, and it's faulty to consider them all the same.

In my case, it didn't matter that much — the unhealed stress fracture showed up, bright white, in the blurry scan. Still, this is an injury I've had for about five months now. It hadn't turned up on two sets of X-rays. Do I want doctors to have the best, clearest vision of what's wrong in my foot, so I can start running again? Absolutely.

That "price shopping free lunch"? It's a mirage.

Knowing what I know now, I'm way more torn on whether I would choose the lower-cost MRI facility.

On the one hand, I did save my insurance plan about $400. If everyone at Vox shopped like I did, then that might do a lot of work to reduce our premiums. That would probably make us all pretty happy! My slightly blurry scan was still enough for my doctor to diagnose the fracture, although I still don't know if he'd have seen something else on a clearer image.

At the same time, my own experience convinces me I've downplayed the trade-offs inherent in shopping for even basic health services. If I went back and did it again, I probably would have gone to the academic medical center for the scan. Because when it comes to health care, I'm selfish — I think most of us are. I want the best shot at fixing my foot, even if that means adding a few pennies to my co-workers' premiums (sorry!).

Recently, I wrote about a new study looking at 75,000 patients who switched from a no-deductible plan to one requiring $3,750 in spending before the benefits kicked in. It showed that even with that really high deductible, patients didn't shop on price. Instead, they saved money by just going to the doctor less.

One economist who contributed to the study described the finding as "surprising," and I agreed: When patients have to cover the full cost of their health care, why wouldn't they look for a better deal? I even called out MRIs specifically as an area where you'd expect to see price shopping but didn't.

My own health care experience is far from unique. But it was a helpful, first-person demonstration of how shopping for health care might not be a zero-sum game, and that even with basic services, there can be clear winners and losers.