Spreading out the purchase via "dollar-cost averaging" is good if you want to buy over a period of time, but if you have money to spend now, it is better to buy all at once now, rather than waiting while the price goes up.
I think your missing the point of dollar-cost averaging though... the whole idea is that you have literally no clue if the price is going up or down, so you spread the risk over days. If we knew 100% market was going up of course dollar-cost averaging is not as good. With commissions being % based, it eliminates the barrier to entry that dollar-cost averaging usually entails
1. The point of dollar-cost-averaging is to avoid trying to time the market. That's why you buy fixed amounts at fixed times. The point is not to reduce risk. There is a more effective way to reduce risk: diversification.
2. You
do have a clue (or at least you think you do) about which way the market is going. Otherwise, why would you be buying bitcoins? If you believe that the price is going up, then obviously the longer you wait to buy, the less you will make.
1) When focusing down to buying into one 'stock', timing the market is the main risk. The whole point of dollar-cost-averaging
(When you already have the cash as OP stated)is to avoid the risk of a bad entry time. Of course, if you don't have the money up front it is used as a way to slow accumulate wealth.
2) Of course buying bitcoin in the long run you are assuming a rise, but I meant short term. Lets say you bought 9 coins when it was near $500 a month ago. Just now you would be about breaking even. But if you bought 3 before then, 3 at 500, and 3 after, your average may be only 350. Where you then already made money, because in the immediate term you negated the risk of poor entry time.
In a larger scale, what if you were someone who has bought 1 bitcoin every month over the last 2 years versus someone who bought 24 bitcoins when they were $1400 a piece. Again, even if in a year the price is 2000 a coin, the person who dollar cost averaged will be alot happier because his average price is lower. thus reducing the "risk" of a poor entry time. I mean in OP's scenario it's not like buying it over time would give him any benefit outside of that
Sorry to intrude...