But if you can afford it, there are 40+" 4k and 8k monitors to which you can plug AppleTV/Chromecast/a small PC with a budget discrete graphics card. Or you can get a conference projector if no monitor on the market meets your size needs.
That's a myth, even if subsidies do exist. Monitors were always more expensive than similar size TVs because they have better specs, more features, and longer warranty.
Linus Tech Tips on the subject: https://www.youtube.com/watch?v=aWH1zXmFgl8
1997 Baltimore Sun article about this: https://archive.ph/mhxET
However, the video you linked doesn't really address the advertisement subsidy point at all (I searched the transcript for any references to make sure), so it isn't really an argument that the ad-subsidy is a myth. Plenty of reporting and discussion and evidence that traditional TV advertising industry (untargeted cable/broadcast ads) is declining in revenue, but the overall TV ad industry revenue is growing (share taken up by smart TV and streaming service ads) is going up. Streaming services absolutely use platform data where they can access it (ie smart TVs). A 1997 article sounds like it would have no context whatsoever about the 2020 smart TV advertising landscape (very very different from traditional TV advertising).
Ad revshare is just so lucrative, especially for ~$0 cost/unit for the manufacturer that it pays for every smart feature and onboard computer and then some. The difference in cost for net-comparable features is still apparent — the cheapest monitor at size-resolution combo X with worst refresh rate/response time/color accuracy is still more expensive than the cheapest smart TV at X (roughly comparable features).
Your parent post implied that if advertising revenue wouldn't exist, TVs would not be much cheaper than monitors.
There are cheap no-name TV producers in China which sell ultra cheap TVs without them making any advertising revenue.
I don't deny that ad revshare is very lucrative, but it's not the reason TVs are cheap. You can have them both, sell TVs at tiny margin above production cost and get extra ad revshare.
Even between CRT TVs and CRT monitors, they weren't even signal compatible with each other. Maybe with a discrete graphics card that could convert pixels to NTSC/PAL outputs? Was that ever a thing in the 90s? Modems to convert cable signals to VGA output? TVs had scanlines because the signal they received represented horizontal lines as modulated analog signals (+ an analog audio signal) which were displayed back as lines after demod, rather than mpeg-bits received via modulated digital signals which were displayed as pixels. All of this meant that other than sharing the presence of a cathode ray tube, monitors and TVs were quite technically distinct. So yeah, in 1997 there were very good reasons why monitors were more expensive, which have since disappeared as the media world converged on digital transmission + output. TVs and monitors are more colinear in the fundamental tech and protocols today, end-to-end, with the differences mostly being auxiliary or in specs.
IIRC where I grew up, the price differences were even more ridiculous in the 90s but because market conditions amplified the technical differences — a TV was a mainstream household appliance, and anything PC-related was enthusiast/technologist hardware.
There are several no-name monitor manufacturers from China too, and their ultra-cheap monitors are similar in price to the ultra cheap non-ad-revenue-TVs (with similar low quality tech specs usually), or price differences more obviously explained by feature differences.
Buying a smart TV but not connecting it to wifi seems preferable to both of these. It's cheaper in price (than buying a professional monitor), and has superior picture quality (compared to projectors).