Hi,
Welcome to the Forum.
Which is correct, we would have taken a discount on the purchase price or we would have taken a discount to the purchase price? Neither of these seems correct. It is not even clear to me whether you are selling or buying.
Here are some good ways to say this kind of thing.
The seller 'offers a discount' on the price. The buyer 'receives a discount' on the price.
Best wishes, Clive