You get what you pay for, even with gravel. A 'proper' gravel drive would not be much cheaper than block paving and would entail a good depth excavation, laying an exterior edge of brickwork or kerb edgings, hardcore sub-base with around 100mm of concrete. The gravel (usually 6mm in this case) is then rolled into hot tar, with a loose stone topping. Even with the cheaper method, a good excavation is required, with maybe 200mm of consolidated hardcore restrained by solid edgings, before 35mm of 10mm stone is spread. Unfortunately with this application the gravel will always 'be on the move' and will need raking more so than the 'Tar' method. I dont think you will find printed concrete much cheaper than block paving. If you do get a contractor in, try and go on recommendation and view previous jobs - preferably older than 5 years!