That's just not true, there are a ton of monitors under $300 you could very happily use for your DAW.
Now if you're going to do gaming or video and photo editing you might not find that many but DAW usage is not that demanding. As Kriminal said anything HD 1920x1080 will be a good solution. My studio computer runs a 27" at 1080 and it looks just fine.
I'd hold off on 4K for a bit longer unless you want to be that guy complaining that old plugins are too small. Developers such as Synapse are providing large GUIs for their plugins but some developers are still lagging behind.
But I have heard good things about BenQ Monitors and the one you listed looks like a good solution and it's under his budget.
The problem is we don't know what output port his video card or onboard video has such as HDMI, DVI-D, Display Port,VGA etc so it's hard to recommend a particular model. Yes there are adapters but not much sense in buying a new monitor and then have to buy an adapter because it doesn't support your computer's output port.
EDIT: Here's another BenQ. 27" 1920x1080 IPS, 5ms GTG $160 4 1/2 Star rating. I'm not even looking for a monitor and I want one.
https://www.amazon.com/BenQ-GW2780-Optimized-Brightness-Technology/dp/B072XFFQ4K/ref=cm_cr_srp_d_product_top?ie=UTF8