Discussing product with a seller without intent to buy:

While certainly there is no prohibition against entering a store without intent to buy, in order to observe the merchandise, which can eventually lead to one buying it then or in the future, nonetheless, based on the above it is seemingly Biblically forbidden for one to lie and tell the owner or seller that he is interested in buying his product when in truth he is no intent to purchase it [i.e. is there in order to get information as business opposition research, or is bored and is doing so for jest to pass time]. This is aside for the possible additional Biblical prohibition of Ona’as Devarim which is transgressed if one fools a seller into believing that he is interested in buying his product when indeed he has no intent to do so.[1] [However, if one tells the seller that he has no intent to buy the product and he simply wants to know the price, then it is allowed. Likewise, some suggest that a quick question of price without going into details and taking much of his time is permitted.[2]]

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[1] See Admur Hilchos Onah Vegineivas Daas 28; Michaber C.M. 28:4; Mishneh Bava Metzia 58b

Seller is unaware that buyer has no intent to buy: According to Admur, there is possible implication that if the seller has no idea that one is trying to fool him, and he rather believes that he is asking to see if he can afford it, then it is permitted even if in truth the asker has no intent to buy it. [Imrei Yaakov on Admur ibid in Biurim p. 43-44] However, even according to this approach, it would remain prohibited for the person to lie and say that he’s interested in buying the product, and rather the allowance is simply for him to ask how much the item costs without mentioning any interest in buying it.

[2] See Imrei Yaakov on Admur ibid in Biurim p. 43-44; Pischei Choshen 15:5 footnote 15; Hilchos Onah Harei Halachos p. 378-380