They recently, like past 5 years got very moto blog trendy, and also transitioned into the nostalgia honda ct70 fan crowd, so prices have skyrocketed like crazy, they're going 3-5x what they were 5 years ago and definitely not worth it anymore. Still of you're diligent and willing to wait you can still find them under a grand. I'd pay up to 800 for one. But they're fetching more than twice that regularly.
It sucks cuz I love them, the horizontal honda is the most produced engine format ever, its incredibly reliable and excellent power and efficiency. There is a real almost every shifty 4 stroke under 200cc is a clone of that design.. parts are easily found including cheap clone engines (with huge sacrifice to quality)
Its really quite a perfect bike, >100mpg and 50mph, virtually unstoppable and usable for whatever tortures you can imagine.
But now you're not just paying for those superlatives, you pay a giant markup cuz collectors and cool dudes everywhere have caught on