1. It costs 1 galcoin per bit to reserve on-peak bits in advance. (Galcoins are very expensive.)
2. You can reprogram your machine on Vega in advance, using slow, off-peak bits. The costs of reprogramming your machine on Vega to make more efficient use of the on-peak bits are inconsequential compared to the gains when you send on-peak bits, that is, you don't need to worry about the cost of reprogramming your machine.
3. If you wind up not needing all the on-peak bits that you reserved, you can resell the bits you did not use (assuming your computer on Vega uses the appropriate protocols, which is the sort of thing you can set up in advance).
4. The market for bits is very, very competitive; you are allowed to resell fractional bits (including trits, decits, and so on).
5. You make your living by sending lots and lots of data, and your profits depend on your efficiency. Due to the volume of information you transmit, you are risk-neutral in the cost of bits, and thus, very small decreases in the [expectation expected cost] of transmitting a message are worth quite a bit of money to you.