that it somehow drives up the cost of transactions from miners seeking to recoup their costs from their investments?
If they could they would. Miner's are competing against each other. If one passes up a transaction because the fee wasn't too high, another more hungry miner might include it.
But yes, currently Bitcoin appears to have an amount of protection (hashing capacity on the non-evil side) that is incredibly greater than is truly needed for today's levels.
We don't know what our "enemies" are capable of.
On the plus side, the market cap for Bitcoin is still so low that it's probably not threatening enough for them to do something about it. By the time Bitcoin is big enough, it may be too costly for them. With each step that Bitcoin grows, the existing financial system grows weaker as more and more people realise they need to rely less on it, ie Bitcoin grows stronger and the financial system grows weaker. There is probably a pivot point somewhere in the middle where the banks are too weak to mount an attack on a stronger Bitcoin.
