Op yes an average Nigerian can invest in Bitcoin, despite the economic situation which Nigerians are been faced with, Bitcoin investment is not taken all our money, the portion of our funds that adviceable to be used to invest in Bitcoin is our discreationary income and it depends on how is left after we are done with taking care of our essential needs, it could be small thing, I do not think it is right for any average person to give excuses why he is not able to invest in Bitcoin, with good financial management, any average person maintain his or her Bitcoin investment, let's not forget that an average person is either poor or rich, and as long as he has a source where finances flows from, it means his discreationary income can be discovered which is what he needs to invest with.
Despite the economic situation Nigerians are facing, the fact that an average Nigerian can invest in Bitcoin if they have discretionary income should be the main point of discussion. In fact we should abandon the idea that investing in Bitcoin is justified by buying a whole Bitcoin, rather than investing with as much as we can afford to lose. We get advice from many investment advisors that bitcoin investment can be started even fractionally, all that is required is discretionary income, long-term mindset but it is not possible to get 15X or more profit from it very soon.
It is arguable that the average person cannot make an excuse for not investing in Bitcoin, but the investment should take into account the financial situation, risk-taking ability,Also those who have sources of cash will be able to invest in Bitcoin and even find discretionary income to invest from it.
I'm very happy that you see through my view on this topic, what does it take to invest in Bitcoin, to some people they need millions to invest, but that is a very wrong idea, Bitcoin investment is very easy if we understand it, I will say it again, an average person have the capacity to invest in Bitcoin except he has no interest to invest, because if he has, there is nothing much to do than to figure out his discreationary income, no matter the amount, as long as it is what he can afford, there shouldn't be any problem with that, the amount might not be much at first, but no one should joke with the power of little beginnings, start first and do more when there more sources as I said earlier and I think it is th best way to go, since I understand that excuses is the easiest way to fail in life, I do not encourage it.
Let me reference you to two points in this thread that I resonate with, and that I would've used as the center of my push back to your POV.
The things is just that, we cannot overlook our needs to buy Bitcoin because we will be forced to sell the Bitcoin to solve our problems, that’s why it is important to be financially stable before thinking about Bitcoin investment so that you can hold for long.
Do not think you can become wealthy or generate wealth with bitcoin, only see bitcoin as a store of value. That means if you hold 1 million naira in bitcoin, expect the amount of money to be higher than 1 million naira after a long time period.
These points are outstanding. Now, let's first understand something. Let's not kid or lie to ourselves, the only way most average earners can actually be satisfied with their investment is when we make profit, at least 10x—I'm quoting this
guy—and I don't even think that is enough.
Before we go into the theatrics of whether an average earner can "invest" in Bitcoin, what does the average earner tends to achieve from investing in Bitcoin? The most logical and sensible answer is wealth—not just gain, but wealth—or am I wrong? (I'd love to be corrected if I'm wrong though).
Let's say an average earner finally accumulates 0.01 Bitcoin, which is ~1.04 million naira, how long do you think it will take to get 10 Million naira—which is around $10k?
Let's look at the previous ATH, the ATH before that was around $60k, the previous ATH was at $104k+, that's not even 2x meanwhile, the previous did way more than that. This shows the upside movement is shrinking. This demonstrate a diminishing return pattern: as Bitcoin becomes harder to attain and the price keeps increasing, increased input/investment will yield lower profit, because the upside movement is shrinking. For example, if Mr. A buys 10 Bitcoin in the 2017 cycle, their marginal profit will be higher than when they buy in the next cycle despite putting in more investment to get 10 Bitcoins; that's because the upside movement keeps shrinking.
See how it keeps on declining:

In as much as we love Bitcoin and want to invest in it, let's not delude ourselves into reckless indulgence by taking unnecessary risk because we want to be wealthy; rather, let's use it to preserve our wealth. Just as Satoshi said, "Secure our wealth".
And that's why I agree with hypen(-), and karl_3000. So..if you don't have wealth to preserve, investing in Bitcoin now because of profit should be done with caution and a good strategy—even when using DCA. Not just preaching discretionary funds and whatnot, you should really understand what you're getting into and apply an investment strategy that can help you achieve your desired result. So even when saying an average earner can invest in Bitcoin migy theoritically and technically be true, it is impractical and most of the time difficult, especially in Nigeria.