the Prophet forbade artificially inflating prices.  

أَنَّ النَّبِيَّ ﷺ نَهَى عَنِ النَّجْشِ  

"I heard the messenger of Allah say: "No man should urge anyone to cancel a sale he has already agreed upon with his brother so as to sell him his own goods; no town-dweller should sell for a desert-dweller; do not artificially inflate prices; no man should outbid his brother; and no woman should ask for her sister (in faith) to be divorced so as to turn over what is in her vessel (deprive her of her share of maintenance),  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ لاَ يَبِيعُ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ وَلاَ يَبِيعُ حَاضِرٌ لِبَادٍ وَلاَ تَنَاجَشُوا وَلاَ يَزِيدُ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ وَلاَ تَسْأَلِ الْمَرْأَةُ طَلاَقَ الأُخْرَى لِتَكْتَفِئَ مَا فِي إِنَائِهَا  

"No tow-dweller should sell for desert-dweller, no man should outbid his brother; and no woman should ask for her sister (in faith) to be divorced so as to turn over what is in her bowl (deprive her of her share of maintenance)"  

عَنِ النَّبِيِّ ﷺ قَالَ لاَ يَبِيعُ حَاضِرٌ لِبَادٍ وَلاَ تَنَاجَشُوا وَلاَ يَزِيدُ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ وَلاَ تَسْأَلُ الْمَرْأَةُ طَلاَقَ أُخْتِهَا لِتَسْتَكْفِئَ بِهِ مَا فِي صَحْفَتِهَا