As far as I know soldering glasses are for eye protection against lead fume. As a personal experience I have observed some parts of lead with tiny explosion due to heat come out of lead with a smoke trace (I dont know what to call them in english).
There are different glasses with different price.
Which one should be used for soldering safety and in what range of price are they?
Flux spattering is not uncommon and if you're right up close it could spatter in your eye. Fumes are not so much a concern for eyes- more for breathing- and flux fumes, not lead (if you're even using lead-based solder). It's possible that you could get actual solder spattering in some kind of rare situation (trapped liquid or something) but it's very, very rare under normal conditions.
Since the splashes are tiny, existing eyeglasses, drugstore reading glasses or "Home Depot" (hardware/home improvement store) glasses work fine. Price range might be $2 and up.
The ideal kind might be the wrap around type. You can find various types here, for example:
Home Depot USA (in USD)
Home Depot Canada (in CAD)
If you're soldering small parts under a microscope you usually don't require safety glasses, but the objective lens may be protected with a transparent shield.
Glasses were mandatory for soldering work in our university electronics lab.
The lab supervisor was not worried about solder splatter. He was worried about wire offcuts from using side-cutters, which fly around at high speed.
If you don't wear glasses normally, a $2 pair of safety glasses from the hardware store (like the below) will be perfectly adequate. You can also wear them when using power tools around the house, i.e. drills, sanders, saws etc. which can all produce high-speed projectiles.
