There are cheaper versions of what professional dentists use on AliExpress, ranging between 30-150 USD.
I bought these:
https://www.ebay.ca/itm/New-1-Dental-Surgical-Loupes-Glasses-Medical-Binocular-Magnifier-3-5X-420mm-/281832405417?hash=item419e8539a92+ years ago for $24 US with free shipping.
The good features, the 3.5 x magnification along with the generous working distance is just about ideal for soldering. The optics are plastic and the eye-glasses frame is metal and both are of good quality for the low price.
The bad: the plastic binocular holder frame in the front has four independent adjustments,
1. tilt up and down, easy to set.
2. inter-pupil distance with a rack and pinion system.
3. and 4. the individual "telescopes" can be turned inward or outward independently for varying toe-in or cross-eyedness.
All those adjustments interact and the plastic is flimsy and in my unit slightly warped leading to only one difficult to find setting that doesn't result in double vision. Even when dialed in they are easy to get out of alignment. What is worse when you get close enough for your brain to make one image come into focus there still remains the eyestrain effect that something is wrong. I spent the better part of 2-3 hours dicking with this thing before giving up in frustration. Additional point, I have good uncorrected vision for someone in their late 50's but I did develop very mild astigmatism in both eyes 10 years ago, which has stabilized. I don't really need glasses for anything but for exacting detail near vision work I have glasses which sharpen things up. It might be that the small asymmetry in my underlying vision made adjusting these "binoculars" more difficult. In the future I plan to harvest the two tiny telescopes and make my own custom holder that will clip on to those corrective glasses. I don't have much motivation to do this experiment now as I have too many other pressing problems to solve.
I have 2 donegan optisight frames, the newer type that are open at the sides and allow peripheral vision, in which I keep 4 and 7 diopter lenses. Two so I can quickly switch between magnifications. I like these, they don't cause eyestrain and feel very natural, either with or without my corrective glasses underneath. Only problem with the 7 diopter is your face is too close to the work, around 11 cm.