What Merlin has proven is that you can pull in a lot of visitors in the short run on a low budget, but the longevity of these attractions isn't the greatest, so the things you build need constant renewal for the park to stay relevant. 40 years from now, Klugheim will probably still be considered a good enough reason for people to visit Phantasialand if they haven't been there before. By contrast, I doubt that the Walking Dead overlay on X:NWO will last five years at Thorpe (okay, Saw is still around and kicking, but...). Besides, the big coasters are still the major draw for visitors to Merlin's parks, most of which date from before Merlin's days. They simply aren't building as many "backbone" rides for the parks to rely on in the coming years and decades, meaning they need to spend those small sums constantly to stay on top of the game. Stop investing any one year, and visits will plunge. Universal and Phantasialand can afford to take breaks in their investment schedule, since the stuff they've already built is substantial enough to pull people in for annual re-visits.