But who decides the worth? The worth is dictated by a person's desire to acquire said item.
A person offers a product for sale on PW for PKR 1000. Person A offers PKR950 for it. Person B offers PKR975 for it. The seller tells B that he already has offer and he would only sell if B offers PKR1200 or more. B decides to go for it due to his need (whatever it might be). Would the additional money; called profit by some, be usury?
Or to think of something else, a person imports HIDs for 5000/pair inclusive of all expenses and sells for 7000. Is the difference profit/trading or usury? Seeing increasing demand, he raises the price to 7500. Is this legitimate profit, circumstantial profiteering or usury?
Please be aware that my intention is not to pointlessly question or irritate you but to clear some of my own doubts I have had about this topic for past many years through different points of view, hence the structured scenarios.
I myself listen to Quran translation so if you have any specific references, please share. From what I recall, Allah specifically refers to usury and trade as under:
الَّذِينَ يَأْكُلُونَ الرِّبَا لاَ يَقُومُونَ إِلاَّ
كَمَا يَقُومُ الَّذِي يَتَخَبَّطُهُ الشَّيْطَانُ مِنَ الْمَسِّ ذَلِكَ
بِأَنَّهُمْ قَالُواْ إِنَّمَا الْبَيْعُ مِثْلُ الرِّبَا وَأَحَلَّ اللّهُ
الْبَيْعَ وَحَرَّمَ الرِّبَا فَمَن جَاءهُ مَوْعِظَةٌ مِّن رَّبِّهِ
فَانتَهَىَ فَلَهُ مَا سَلَفَ وَأَمْرُهُ إِلَى اللّهِ وَمَنْ عَادَ
فَأُوْلَـئِكَ أَصْحَابُ النَّارِ هُمْ فِيهَا خَالِدُونَ
Those who devour usury will not stand except as stand one whom the Evil one by his touch Hath driven to madness. That is because they say: "Trade is like usury," but Allah hath permitted trade and forbidden usury. Those who after receiving direction from their Lord, desist, shall be pardoned for the past; their case is for Allah (to judge); but those who repeat (The offence) are companions of the Fire: They will abide therein (for ever). (2:275)