Partially inspired by this question I would like to know exactly how ona'a (over/underchanging by more than 1/6th) is determined. For example tap water is free and in many parts of the united states is 100% safe to drink. Yet people pay more than $1 for bottled water. Why? I would chalk it up to marketing. Does that mean that I as an orthodox Jew cannot sell or buy a bottle of water since I would be duping the consumer?

What are the parameters for determining if one person is violating Ona'a?

Note: please don't get bogged down on the example; feel free to provide a better one that demonstrates the question.


Are you misrepresenting the standard going price for this item?

$1 for a bottled water is a fairly common price, given the right convenience and location. If a visitor from another country showed up off the airplane and you told him that you're giving him a discount, normally a bottle of water costs $10 but you're giving it to him for $8, that's ona'ah. Or even: "normally these cost $1 but I'm charging you $8 because you're in a situation where you're desparate" -- reprehensible, but as I understand it, not ona'ah per se.

(I heard Rabbi Yitzchak Breitowitz point out that the common definition of ona'ah doesn't prevent a group of sellers from conspiring to inflate the standard going price; it assumes markets have established standard prices.)

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  • so then one would not be allowed to charge or pay for items in, say and airport or movie theater where prices are inflated due to location? – please remove my account Sep 17 '13 at 17:23
  • @User3120, again, allowed as a reasonable person understands that at a grocery store the normal price for this bottle is $1. You're charging $4 here because of the convenient location. – Shalom Sep 17 '13 at 19:07
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    It would seem then that ona'a is simply a special case of m'dvar sheker tirchak. Essentially you can charge whatever you want as long as you can explain it as being valid due to the circumstances. The only thing you cannot do is lie about those circumstances. Is that correct? – please remove my account Sep 17 '13 at 20:53

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