The amount you quoted, $10 to $15 dollar is actually a big amount of money for some people. According to
this article, the minimum wage in Bangladesh is 14.62 per month. This mean $15 is a big amount of money for some people. So one need a good financial balance to be able to DCA even with the amount you quoted.
Hopefully anyone who is a member of this forum and is ONLY making minimum wage in a place like Bangladesh and/or any other country with similar kinds of low level wages, these people should be working towards increasing their wages rather than merely making minimum wage... and so maybe they should still be figuring out ways to make more and to be able to put that extra money into bitcoin.. . and surely make sure that their monthly expenses are covered so that they do not ever have to sell any of their bitcoin, except at a time that is of their own choosing, and surely many of us even realize that it could take many many years to reach a stack of bitcoin that feels sizable if you are ONLY able to invest $10 per week, which would be $520 per year, which would be $5,200 over 10 years, and so maybe 10-20 years of investing into bitcoin, even with a low amount will start to feel like it is providing a lot of options that had not been available without any kind of investment into bitcoin.
You are 100% right on this. The minimum wage is actually very small but it represent the smallest amount of money the least persons (those without education or technical qualification or skill) earns. Some skilled workers earns as much as $50 per month and higher. The purchasing power of the minimum wage in that country is high despite it being a small amount compared to other countries. However, it is not enough to make decent accumulation of Bitcoin since the later is not in the local currency. For those at the higher echelon, they can actually meet their needs and still have enough money to invest in Bitcoin and these are the people that can apply the DCA method effectively.
Therefore, if one find himself in a country like Bangladesh and even mine, it is important to seek for other means of getting additional funding to be able to invest in Bitcoin.