If the price of the product is no more than the price in other stores, and the purchaser bought it because he needed it and not so that he could enter the draw or contest to get the gift, then there is nothing wrong with it in that case, according to the correct scholarly view.
The different opinions of scholars concerning this issue have been discussed in the answer to question no. 22862.
Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allaah have mercy on him) was asked: Here in Kuwait we have different kinds of transactions that are widespread nowadays. The businessman offers his products and distributes coupons to the purchasers according to how much each of them spends. These coupons are entered into a draw for prizes, then after that the draw is made and some people win prizes given to them by this businessman. What is the ruling on that, may Allaah reward you with good?
With regard to this kind of transaction, we must address the seller and the purchaser. To the seller we say: did you raise the price because of this prize or not? If you raised the price, then this is not permissible, because if the price was raised and the people bought from him, then they will be either winners or losers. If the market price for this item is ten, for example, but you made it twelve because of the price, then this is not permissible, because the one who bought it for twelve will either lose the extra money that he paid, that was more than ten, or he will gain more than that amount in the prize. So this falls under the heading of gambling, which is haraam.
If the seller says: I am selling it at the price that people usually pay, no more and no less, then he may offer those prizes so as to encourage people to buy from him.
Then we turn to the purchaser and say: Did you buy this item because you needed it, and would you have bought it whether there was a prize or not, or did you buy it only because of the prize? If he says the former, then we say there is nothing wrong with buying it from this vendor or that, because so long as the price is still the market price, and you are going to buy this item because you need it, then in that case you will either be a winner or be safe. In that case there is nothing wrong with buying it from the one who is offering prizes.
But if he says, I bought it although I do not want the item; I only bought it so that I could get the prize, we say that this comes under the heading of wasting money, because you do not know whether you will get the prize or not.
I have heard that some people will buy a carton of milk which they do not want; they buy it and pour it away in the hope of wining the prize. This is wasting money, and it is proven that the Prophet (peace and blessings of Allaah be upon him) forbade wasting money.
There remains a third matter, which is that someone may say that this transaction may harm other sellers, because if this seller offers prizes to purchasers, and his prices are like the market prices, all people will go to him and the sales of other traders will become stagnant, so this will harm others. We say: This matter should be referred to the state, which should intervene. If the state thinks that this matter will affect the market, then it should ban it if it thinks that banning it will be in the people’s interests, or if it thinks that it is tinkering with the markets, because tinkering with the markets is something that the authorities should prevent.
End quote from Liqaa’aat al-Baab il-Maftooh (49/question no. 5)
It makes no difference whether the prizes are offered to the one who wins the draw or to all purchasers, or whether they are the same or differ according to the draw or how a person plays the game, as you mention. All of that is permissible subject to the two conditions mentioned above.
And Allaah knows best.