3) We collectively pay miners 7200 BTC per day to secure the network.  At $3, that's over $20,000 per day.  At $30, that's $200,000 per day.  That money has to come from somewhere - and if you're the one manipulating the market to keep it that high, you're the one who ends up paying for it.  Unless you have a really good reason why the price needs to be that high, that's wasted money.  (A price boom creates a mining boom, which creates a hashrate boom until mining profits reach about current levels; once it settles out most of that $200,000/day gets spent on electricity.)  The current level of economic activity does not justify that level of blockchain security.