If an amount like $20-$30-$40 can be invested continuously in the DCA method, then it can become a very large asset over time, in fact, the amount of investment does not matter here, here the most important thing is to deposit Bitcoin continuously with long-term faith, you can keep buying Bitcoin continuously with any amount of money according to your ability, but it can become much bigger than your expectations over time, because the chances of success of Bitcoin are very high and the future of Bitcoin is bright.
I agree with you that the amount is not important, but holding it in the long term is the most important thing. The real proof of this is that those who spent only $10 on Bitcoin at the beginning of Bitcoin and held it until now are at what level today? They have certainly become the owners of a lot of money today, although the number of such people is very small.
Maybe history is not possible to repeat itself in the future. We may not be able to profit so much in the future, but if you trust Bitcoin and hold it for the long term, you may not lose, but you may profit more than you expect. Without delay, even if you have a little discretionary money, try to be consistent in planning for the long term. However, a very small amount may not be investable.