Buyer side: Having the regulatory approval will most likely increase the price. If you have already negotiated a price pre-regulatory approval, then the seller cannot increase it.
Property example: If you are selling land, and Buyer 1 is a house builder and has the intention to build 1000 flats on it to sell for £250K each, they may put in a bid of £X. The seller may think, the offer from Buyer 1 is great, Ill take it. Buyer 1 then goes out to get planning permission (costing them time and money), and after 6 months they get it. Now, they know they will rake in the money once they have built the flats, However, the seller now feels they have sold it too cheap and want to go out to tender again with regulatory approval that was granted. Seller now wants £2X.