How much would you pay for a used electronic that would normally sell for $200?

$50 to $75 if they are under three years old.

It depends how much they are used. If they are called “used” for official purposes only, or if they are so used they die after a month.

Depends on the shape they’re in. If they were relatively new, I wouldn’t mind paying half of that, if not a little more. But if they’ve obviously been through a lot of use, at that point it’s not even a matter of what I would pay for them, rather than that I’d look for something else.
Unless they’re a really rare model that I want and believe that I probably won’t find anywhere else, but I hardly doubt that would come up with something like speakers or a TV, because there’s always some higher and more recent model I could consider. (I would only consider paying some crazy price for a very used item if it was some discontinued video game, or something like that)

Do you know the musical habits of the current owner? If they play loud stuff all the time the cones will have degraded. If they play pleasant granny tunes all the time at moderate volume they should be nearly good as new.

Also there is the consideration of cosmetics. Are the cases damages at all?
$200 is not a lot for speakers new, so they are probably not studio monitor quality in the first place.

Will you be able to try them out before you buy them?

Without additional info I’d ballpark about where @zenvelo does, $50 to $75…

I would have to hear them before I would venture a guess at price. That being said, I would pay 50 to 75 dollars.

If they were not abused, then there is no reason that they should too cheap.

It would depend on how difficult they are to come by, how badly I need/want the speakers and how much I have to blow on speakers.