Don't nurse grudge and don't bid him out for raising the price and don't nurse aversion or enmity and don't enter into a transaction when the others have entered into that transaction and be as fellow-brothers and servants of Allah. A Muslim is the brother of a Muslim. He neither oppresses him nor humiliates him nor looks down upon him. The piety is here, (and while saying so) he pointed towards his chest thrice. It is a serious evil for a Muslim that he should look down upon his brother Muslim. All things of a Muslim are inviolable for his brother in faith: his blood, his wealth and his honour.  

قَالَ رَسُولُ اللَّهِ ﷺ لاَ تَحَاسَدُوا وَلاَ تَنَاجَشُوا وَلاَ تَبَاغَضُوا وَلاَ تَدَابَرُوا وَلاَ يَبِعْ بَعْضُكُمْ عَلَى بَيْعِ بَعْضٍ وَكُونُوا عِبَادَ اللَّهِ إِخْوَانًا الْمُسْلِمُ أَخُو الْمُسْلِمِ لاَ يَظْلِمُهُ وَلاَ يَخْذُلُهُ وَلاَ يَحْقِرُهُ التَّقْوَى هَا هُنَا وَيُشِيرُ إِلَى صَدْرِهِ ثَلاَثَ مَرَّاتٍ بِحَسْبِ امْرِئٍ مِنَ الشَّرِّ أَنْ يَحْقِرَ أَخَاهُ الْمُسْلِمَ كُلُّ الْمُسْلِمِ عَلَى الْمُسْلِمِ حَرَامٌ دَمُهُ وَمَالُهُ وَعِرْضُهُ