[sporkmonger]

I used 0.0005 BTC (~5kb), but you're absolutely right that a simple transaction is substantially cheaper. My assumption here is that as the economy grows, due to the underlying technology of Bitcoin, more BTC will need to be 'gathered' together in a wallet before being sent out. This results in a larger transaction size and a higher fee to exceed the priority threshold.

I suspect that in the future, this will be a fairly common case. I suppose I might liken the theory here to defragging a hard drive. An unused hard drive stays in a nice neat, contiguous state. But use it a whole bunch and things get messy. And in BTC's case, you have to pay a bit extra for the miners to come along and tidy everything up.

I could be totally wrong on whether that will ever become common, and the developers could just as easily reduce fees over time as well, but such is the nature of taking guesses at the future.