Do Costly XLR Cables Make A Difference?

It depends how resolving your setup is and what you’re looking for in a new cables. 
I recently borrowed Kimber KS1136 and Audience AU24SX to compare with my Acoustic Zen Absolute Copper. Every set had a unique sound signature. I was pretty sure the AU24SX would be a better fit since I am using the AU24SX speaker cables but after days with each set, I ended up keeping my AZ Absolute Copper. 
I also ran Mogami Studio gold between pre and amp for about a month. While it worked well, in the end the Mogami weren’t on the same level. Back went the AZs. 
I’m not trying to tell you to get AZs. All I’m saying is you need to listen in your own system. Do what I did and borrow from the cable company. 

@jaytor

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I could not discern much difference between relatively inexpensive cables (e.g. Mogami) and more expensive cables for these short connections, but the differences were much more apparent with the 7M connections.

I believe it. The most likely explanation is the interconnects you use between preamp and amp(s) are what influences the sound the most. I was in the same boat when I moved my front end components to the side wall and ran a 15ft Mogami XLRs to my amp for a month or so. It was not even close to what the AZ Absolute Copper sounded like. During that time I tried different interconnects and power cables on the source components and the Mogami were always the bottleneck in realizing the improvements brought by those changes.
I ended up moving everything back to be able to use my 1m AZs between the pre and amp again. Way more benefits using higher quality cables than removing a 5 shelf vertical rack from between the speakers. Now if the AZs weren’t so expensive for a 5m set it would’ve been a no brainer.

@lalitk that’s exactly the next step I plan to take. Position components in a horizontal fashion between speakers as low as possible.