Bitcoin is obviously an expensive investment, most especially if you are trying to accumulate the whole piece of it. But if you are trying to do dollar cost average regardless of the amount, you will not feel the expensive price anymore as you are only investing every now and then the amount that you can afford to lose.
However, the only thing that you should worry is that if you are not patient enough to hold for that long term. DCA will be useless if you suddenly resort into panic selling everytime the market is crashed due to market price correction.
In fact, the DCA model will indeed prevent you from panic selling, but additional capital is also very necessary, otherwise how can we consistently accumulate every drop of BTC if we don't have sufficient funds as you mentioned above.
Regarding profits in BTC, it will show itself because I am sure that everyone can record it, even if they only buy $20 using the DCA technique, regardless of the price increase or decrease.
Many people make too many mistakes and DCA would allow people to have a sense. The biggest issue in the bitcoin world is that when the price is going down, way too many people are selling, the whole reason why it keeps going down is people keep selling, so when you get to start doing DCA, that means you are going to buy when it goes down. It basically prevents the whole drop thing, because when price goes down, instead of selling and losing money, you are buying and making profit later on.
This is why it's such a great method and I do suggest every newbie to do it. I have been buying for years, and sometimes I sell because I need the money, but rarely have I ever made a loss, it's been like once or twice at most, rest of the time, even though I urgently needed the money, I was always in profit. That shows you that DCA is such a good method that even at times when you shouldn't sell, it may actually still be a profit for you and that's a great thing.