What is the ruling on accepting a sum of money from a major company to withdraw from a bid, or to price it at a price determined by the buyer to ensure he gets it, knowing that he did this with other companies?

It is forbidden for participants in a tender or auction to collude, whether for a fee or not, because it involves deception and harms the tendering party. The objective of a tender is to obtain the lowest price. Sheikh al-Islam Ibn Taymiyyah mentioned that if market participants agree not to bid up the price so that the seller sells their goods for less than their true value, this harms the seller.

The Permanent Committee for Issuing Fatwas was asked about the collusion of buyers in an auction to prevent price increases. They replied that it is forbidden due to the harm it inflicts upon the owners of the goods and unnecessary price manipulation. This is akin to talaqqi al-rukban (meeting riders outside the city to buy their goods before they reach the market price) and bay' al-hadir lil-badi (an urban dweller selling on behalf of a Bedouin), both of which the Prophet (peace be upon him) forbade due to the injustice and resentment they generate. The seller has the option to annul the sale if it becomes apparent that they have been defrauded.