Of course they've had to pay. In the case of the investors, they've had to pay cash up-front to fund the development of Zcash. In the case of other shareholders of Zerocoin Electric Coin Company, they've had to pay for, or otherwise legitimately obtained their shareholding -- for example by their labour, in the case of developers who are also shareholders.

"Pump and dump" means fraudulently manipulating the price of a stock by making deliberately misleading or inaccurate statements in order to sell it at a premium. That's illegal under securities law. If you invest in something that then increases in value over a long period because people generally think it is valuable, and at some point you sell it, that is not "pump and dump".

Declaration of interest: I'm a Zcash developer and I hold some shares in Least Authority, which owns part of Zerocoin Electric Coin Company.