Seriously??? Why would someone want to acquire an old CRT Monitor nowadays???
You cannot plug a DOS PC into a modern monitor that easily, because the upscaler board doesn't support VGA resolution. They seemingly don't handle anything below VESA (640x480). It is common to plug a HDMI port from late 00s PC into a modern monitor only to have no picture until the Windows or other OS kick the card into VESA modes.
If by any chance you can, the monitor doesn't have right aspect, 4:3 and it will have black margines. And then comes the worst part - LCDs have upscalers in them which are devices that sit on the input stream and transform it into a picture for the LCD matrix - this takes some time. On the actual DOS PC, in a tightly written game, the time between keyboard press and visual result on the monitor is down to 1000s of a second. On the graphics card, there is a device called video generator, that grabs pixels from video memory and generates video signal(s) that drive the monitor at the speed of light. There is no data, no streams or packet standards, only electronic signalling.
Emulators and modern stuff all suffer from this. The accuracy of an emulator is not an issue, the issue is USB HID latency and display latency.
This is all not considering the innate advantages of CRT vs LCD e.g. natural lighting and dimming of the pixels which produces a far stable picture.
Keep in mind, it is not easy to sell a monitor. And it's not actually easy to buy one cheap or get it for free. It's a niche. I'm just saying its cool you still have it, stick to it. Ebay prices can look tempting, but it takes investment to become an ebay seller.
Personally I was left without any CRTs as I didn't see the benefits of sticking to one back then, so I had to regenerate my stash.
I paid around 100 euro plus ship for each of two branded VGA monitors from the late 80s. These are rare, and match the OEM systems.
I paid around 40 euro for a 90s branded VGA monitor - but I had to organize delivery from another city.
I paid nothing for the best of them - a mid 00s 17" SyncMaster with still great picture that can do 800x600 in 100 Hz, a friend had it in a garage ever since upgrading to first LCD.
On top of this you have people that buy 19" but want to end on 21" the best CRTs out there, profi ones, to do actual 2026 gaming on them because the games look better than on anything I've ever seen. LCD is tech for a calculator display not for vivid images.
Then there is a whole category of people buying PVMs, the CRT monitors used in video racks to monitor video feeds, mostly by Sony. These are small, expensive, but they cover almost any video standard out there. Earning gamers mostly use these - I've watched a lot of a guy that does a Super Nintendo game renowed for its speedrunning complexity, 2 frame perfect, pixel perfect tricks. It's not actually possible without a great CRT screen.