Legendary Projects

I noticed that, the more legendary Projects have been completed, the more coins need to be collected in Order to receive one speed-up coins. This ist quite senseless. Consider this:  I have maybe 45 legendary buildings which produce Bronze coins, I now need 14 such coins in Order to get one Bronze speed-up coins. When I Had 40 legendary buildings with the Same Production, I needed 12 or even less Bronze coins for one speed-up coin. If I build one or two more legendary Projects, I'll need 17 coins for one Bronze speed-up coin, and get less speed-up coins in total, even though I have more legendary buildings. So there ist No Point in doing more legendary Projects. I can never be Sure that I will be able to get the 100 legendary Points for a silver coins building. Hence I don't do legendary Projects any more.