The digital map still has to be surveyed, checked, drawn, (however this is done) .this takes skilled labour which is not free. The printed map is then produced from the file. The only saving for the seller of a digital map is the actual printing. If you çan't afford to buy it, then get an app using open source maps.
That will set you back about thirty notes but you probably won't be able to print from it. Carry a spare battery, eh?