ViewSonic sells plenty of FreeSync monitors, like the XG240R we reviewed earlier this year. For the rest of today, the company's 'VX2458-MHD' display with 144Hz FreeSync support is just $142.99 on Amazon. That's $37 off the original MSRP.
This specific model is 144Hz, with a 24-inch TN panel and a resolution of 1920x1080. There doesn't appear to be many reviews of the monitor, and we haven't tested it ourselves. In addition, it's not officially supported by Nvidia's G-Sync compatibility program, but it may still work with the latest Nvidia drivers.
All that being said, user reviews on Amazon are mostly positive, and 144Hz 1080p monitors aren't common at this price point.
Some online stores give us a small cut if you buy something through one of our links. Read our affiliate policy for more info.