Talking about the amount of investment, it really comes back to each individual because he will do it according to his abilities, indeed the monthly amount is quite large and the average standard salary in several countries is indeed not enough for that, but if he has a good position in his job, he will definitely able to do it.
In my view, collecting bitcoins at a total price of $ 20 / day is of course an inappropriate strategy in my opinion, because it will take a lot of transaction fees which are quite hefty if collected, it is better to extend the purchase interval, for example once every 2 weeks or once a month with a total amount the same one.
For example $ 20 X 14 days (two weeks break) = $ 280, and he only makes 2 transactions to make purchases in one month, in my opinion this method is more effective and economical for buying bitcoin.
Someone can do without coercion in their minds to be able to buy at the nominal rate they specify because the direction of urgent needs makes the situation quite complicated for our finances, but we can do it regularly with a different nominal investment rate from week to week.
Previously I thought those who did long term would not be a problem for them if they missed a few buying periods due to financial instability. However, they will resume buying when their finances stabilize.
I hope you read what started my post first, I referred to what @armanda09 said, because he decided that it is better to save bitcoins with an amount of $ 20/day than to do social gathering.
I agree with you, when it comes to the issue of quantity, because it is a dynamic and fluctuating matter, because everyone who has a stable income doesn't necessarily have stable needs, sometimes they go up and down.
That's true, those who miss several periods of buying don't matter if the goal is long term in accumulating bitcoins because it's true as you say, and they can continue at a later time when they find enough stability to continue their bitcoin accumulation.
But what I'm trying to suggest is for the main point of the point is, if someone has the intention of accumulating bitcoins every day for a certain amount, it is not effective, because it is based on transaction costs, which you might be able to take as an additional investment if you reduce transactions to make purchases, although only accumulated from all fees 1-5 dollars.