DeWalt are good and so is Makita.
In general you are paying the money for the batteries. For example, I live near the DeWalt factory and they have a factory outlet.
You can buy a 14.4v cordles hammer drill driver from there for £40. The batteries cost £60 each and the charger is another £40.
Hence why the drill with two batteries is normally over £200.
Cheap drills have cheaper gearing and motors but its mainly the batteries where you suffer. My DeWalt ones last for ages and recharge in an hour.
I have seen websites if you google them which show with cheaper drills that if you break open the batteries they are just 1.5v small batteries in series to generate the necessary 14.4, 18v 24v etc. Proper batteries are not like this.
I have a cheap b&Q set which I bought as it was on offer for £50. Cordless drill, lamp, circular saw and 3 batteries. The torque and power that these produce is nothing like my DeWalt stuff. You can feel the DeWalt drill turning in your hand when you power up.
My suggestion is don't skimp and check out Ebay as well. I picked up a DeWalt cordless circular saw for £45 on there with two 14.4v batteries so now I have 4 batteries and two chargers. It was worth £45 just for the two batteries tbh,