What is the ruling of shill bidding on ebay?

In the Name of Allah, the Most Gracious, the Most Merciful.

As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.

The Answer:

Shill bidding has been explicitly prohibited by the Prophet ﷺ.
Shill bidding or artificial bidding is against the policies of eBay.  To breach an agreement after agreeing to it is not permissible unless there are exceptional circumstances.

The jurists have categorically stated that shill bidding in order to inflate the price over its market value and worth is severely disliked.  To engage in such a practice and to prompt others to participate in such activity is sinful.[1]

And Allah Ta’ālā Alone Knows Best

Mufti Faraz Adam,
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[1]  (وَمِنْهَا) النَّجْشُ وَهُوَ أَنْ يَمْدَحَ السِّلْعَةَ وَيَطْلُبَهَا بِثَمَنٍ ثُمَّ لَا يَشْتَرِيهِ بِنَفْسِهِ وَلَكِنْ لِيُسْمِعَ غَيْرَهُ فَيَزِيدَ فِي ثَمَنِهِ وَإِنَّهُ مَكْرُوهٌ لِمَا رُوِيَ عَنْ رَسُولِ اللَّهِ – صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ – أَنَّهُ «نَهَى عَنْ النَّجْشِ» ؛ وَلِأَنَّهُ احْتِيَالٌ لِلْإِضْرَارِ بِأَخِيهِ الْمُسْلِمِ وَهَذَا إذَا كَانَ الْمُشْتَرِي يَطْلُبُ السِّلْعَةَ مِنْ صَاحِبِهَا بِمِثْلِ ثَمَنِهَا، فَأَمَّا إذَا كَانَ يَطْلُبُهَا بِأَقَلَّ مِنْ ثَمَنِهَا فَنَجَشَ رَجُلٌ سِلْعَةً حَتَّى تَبْلُغَ إلَى ثَمَنِهَا فَهَذَا لَيْسَ بِمَكْرُوهٍ وَإِنْ كَانَ النَّاجِشُ لَا يُرِيدُ شِرَاءَهَا وَاَللَّهُ عَزَّ وَجَلَّ أَعْلَمُ. (بدائع الصنائع)

(قَوْلُهُ فِي الْمَتْنِ: وَكُرِهَ النَّجْشُ وَالسَّوْمُ إلَخْ) قِيلَ لَمَّا كَانَ الْمَكْرُوهُ أَدْنَى دَرَجَةً مِنْ الْفَسَادِ وَلَكِنَّهُ شُعْبَةٌ مِنْ شُعَبِ الْفَسَادِ أَلْحَقَهُ بِالْفَسَادِ وَأَخَّرَهُ عَنْهُ. اهـ. أَتْقَانِيٌّ وَكَتَبَ مَا نَصُّهُ قَالَ الْأَتْقَانِيُّ وَالْمَعْنَى فِي كَرَاهِيَةِ النَّجْشِ الْغُرُورُ وَالْخِدَاعُ. اهـ.(حاشية الشلبي على تبيين الحقائق) 

رَجُلٌ اسْتَامَ مِنْ رَجُلٍ شَيْئًا بِثَمَنِ الْمِثْلِ فَزَادَ رَجُلٌ آخَرَ فِي الثَّمَنِ لَا يُرِيدُ شِرَاءَهُ وَأَنَّمَا يَفْعَلُ ذَلِكَ لِيُرَغِّبَ الْمُشْتَرِيَ فِي الزِّيَادَةِ فَذَلِكَ مَكْرُوهٌ وَهُوَ النَّجْشُ الْمَنْهِيُّ عَنْهُ، وَإِنْ كَانَ الَّذِي اسْتَامَ يَطْلُبُ الشِّرَاءَ بِأَقَلَّ مِنْ قِيمَتِهِ فَلَا بَأْسَ لِغَيْرِهِ أَنْ يَزِيدَ حَتَّى يُرَغِّبَ الْمُشْتَرِيَ فِي الزِّيَادَةِ إلَى تَمَامِ قِيمَتِهِ وَهُوَ مَأْجُورٌ فِي ذَلِكَ كَذَا فِي فَتَاوَى قَاضِي خَانْ. (الهندية)