I think it's because people are buying coins in ico for pure speculation, not because they really consider those coins good long term investments. 200% profit in a few days was possible some time ago, but now there are way to many ICOs. This is why you should invest only in coins having long term potential. Just check the quantity of coins released during the ico and if it's too big, wait for a few weeks, you might get the coins for lower price than the ico price:
RE: Possible reasons on why TenX(PAY) price has dropped. Quick look at TenX