Rationale:
1. You will (over time) benefit from the daily fluctuations in price
2. Assuming the buys are made on an exchange the only fees will be the exchange fees for each buy - these are likely to be on a percentage basis and therefore indifferent to one $1400 buy or seven $200 ones;
3. withdrawals to your wallet can be done weekly or monthly as you prefer to minimise network transaction fees
If you do Dollar Cost Averaging, you won't care too much about fluctuation.
Of course you do - its the whole point of buying on a DCA basis: you recognise that the price varies up and down (i.e.
fluctuates) and so you spread your buys in order that sometimes you benefit from buying at a lower price. If you didn't care about fluctuations in price you may as well just use your entire investment in one go and not bother to cost average.