Partially true.  Actually there is a connection, but it is the opposite: price causes the cost because of competition.  That was one of the main points of the article in the OP.  Competition will always rise to spend as much resources as possible while still making a profit.  Maybe that is not the intention if the design of the poS coins, and maybe that isn't happening right now, but so far no one has been able to say why that wouldn't happen if there was a serious Bitcoin contender with a widely distributed stake.

@Jabo38, you are correct that the transaction volume needs to grow by orders of magnitude to maintain the same level of security with no block subsidies.  However, we have decades to get there, and even if the hashing power dropped by a full order of magnitude Bitcoin would still be secure.