Best XLRs under $500 a pair

Avoid anything with PVC. 

My approach was buying used XLRs from Kimber Kable via KimberKabledirect on eBay.

I tried the Kimber silver streak versus some Mogami and better cable silver serpent and the Kimber's were noticeably better and also about 4 times the price.  

So I searched Audiogon for used cables and looked at eBay and found Kimber very active in selling trade-ins and demos via eBay at about 1/2 list price.  

I purchased KCTG 1 meter and .5 meter XLRs and I view them as my forever interconnects.

A little over your price point, but great cable. Shadow 2 is a pure silver cable at the middle of Dynamique Audio line. I own both the Shadow 2 and Zenith 2 and I'd say the Shadow performs above 80% of the top of the line.

Look into Acoustic Zen Matrix Reference II and Audience AU24 used close to your price range. You got other good suggestions here as well. 
Throw a dart for the choice between the Benchmark, Mogami Gold(similar star quad design) and Belden 1800f all with neutrik connectors. 

Kimber Kable Hero.