CRTs are large, heavy, highly complex and potentially dangerous machines that haven't been in production for 15+ years. Many are hitting the 30 year mark. The odds of them failing gets higher every day. Unless you're skilled in CRT repair, this needs to be taken into consideration. $100 USD is generally considered the maximum reasonable price for a CRT. Even then, it would have to be particularly rare or in great condition. An average consumer CRT is worth about half that at most.
Screen size also matters. CRTs in the 20-24 inch range tend to go for the most money because they hit that sweet spot of being large enough for the average person to enjoy while not being too heavy. Smaller CRTs have more niche appeal, and larger ones can often be had for free because moving them requires two or even three people.
Brand name generally doesn't affect the price, at least for consumer CRTs and PC monitors. Sony, JVC, Panasonic, Ikegami, Mitsubishi, and Magnavox are all fine brand names. When you get into professional CRTs, then it starts to matter. The famous Sony PVM has amassed a cult following online, driving an already rare and expensive line of CRTs into the realm of unobtanium for the average hobbyist.
Beware of listings with "retro," "vintage," or "great for gaming" in the title. Sellers who include those buzzwords are often asking well over $100. Every CRT, even tiny black and white ones, can be "great for retro gaming" in the right hands. Don't let yourself get scammed. For every listing asking $150, there's another giving it away for free.
Please don't give into the temptation to buy one on eBay. Those prices are often the highest of them all, soaring above $200-300 before shipping. It may be convenient, but paying that price tells sellers they can continue charging that price, so you're indirectly hurting every other member of the community. If rich nerds would stop paying hundreds of dollars to avoid social interaction, there would be no market for ancient and otherwise obsolete televisions. The prices would plummet, making them much more affordable, leading to more CRTs in the hands of people who appreciate them. Not to mention shipping a CRT is something of an art. There's a high chance the seller will do a poor job packing it and it may arrive broken.
The ideal thing to do would be to decide on a screen size and your prefered video input (for example, a 14 inch screen with an S-Video input, or a 20 inch screen with a Component input), and then look at local listings. Try Craigslist, Letgo, and other local selling apps. (If you think you need more than one input, remember you can always get a switcher.) Find a listing close to you that meets your criteria for no more than roughly $50. Once you find one, you should ask for a picture of it displaying an image if one is not provided, or at least the model number, so you have some idea of what you're getting before you buy.