Let's say bitcoin gets to $1M a coin in 2140 after all block rewards have been exhausted. The current fees we're seeing now are .2 btc (one recent block just had 3+ btc in fees). At $1M per coin, the $200k reward would be substantial more than the 6.25 + .2 (~$175k) that the reward is today. I don't think BTC's price going to $1M per coin is outlandish by any means. In fact, it's probable in my opinion. So, I understand the security budget concerns, I just don't necessarily put that much stock into them.