Any investor that does not have a discretionary income does not need to invest in bitcoin because if he does, it means that he is gambling and he will definitely run at loss because that is always the outcome of gambling.
I agree with you. But I cannot agree with the comment that one should not invest if there is no discretionary income. Nowadays there are very few people who cannot save $25-$35 after meeting their monthly needs. Out of necessity people work hard but earn extra money. Nowadays people thinking about their future keep their fiat in a savings account in banks or various NGOs. I think investing in bitcoins might be a better choice than putting money in this savings account. Because Bitcoin savings offer higher returns than bank savings, Bitcoin savings tend to last longer than bank savings. I wouldn't say to invest the entire savings in Bitcoin. You can easily start investing in Bitcoin by investing $25-$35 i.e. $10 out of $30 in Bitcoin, $10 in bank savings and $10 in an emergency fund. $10 is a small amount but very beneficial for low income people. If you have less than $10 to invest, you can start investing by saving $20 every 2 months. If one can successfully extend his investment for at least 4 years then after 4 years he can save 12×4×10=$480, calculating the profit from this due to increase in value of Bitcoin he will easily get back $700-$800. Where he can connect some money and find a small source of income.
Your various formulas sound like short term trades, rather than investing, esepcialloy to the extent that you don't seem to be describing holding for more than 4 years.
on the other hand, if you are talking about holding those amounts and continuing to accumulate more than 4 years, then you are referring to using discretionary income (money that you do not need because your expenses are already covered for 4 years or more.
Don't get me wrong I would not be recommending anyone with those kinds of relatively low amounts to be investing into bitcoin for ONLY 4 years, yet there are people who are older or maybe have health or life circumstances that might not allow them to invest into bitcoin for much longer than 4 years, so there could be some folks who are barely meeting the 4-year minimum threshold in order to consider their entrance into bitcoin as an investment.
Another thing is that it is not guaranteed that whatever you put into bitcoin will be in profits, even in 4 years, and you (Jewan420) seem to be describing a kind assured profits, even after 1 year, so you surely sound like a gambler or a trader rather than an investor and your expectations of profits seem a bit too strong and/or unrealistic. In other words it is possible that you BTC investment goes lower or even goes to zero whether we are talking short term, or medium to long term or even 4-10 years or longer or whatever timeline, so that should also be considered with any money that is put into bitcoin - and yeah, sure people can do whatever they like, even seemingly erroneously presume that their investment (or trade or gambling play) into bitcoin is going to be in profit in whatever timeline that they are projecting that they are going to need (or want) the money.. and surely another sign that you are not using discretionary money to invest into bitcoin is that if you believe that you need the money at some point in the future, since it seems more healthy to consider that you might never get the money back, even though surely almost everyone invests into any investment because they are considering the odds for UP to be greater than the odds for DOWN, and so even if profits are not guaranteed, they are considering their placement of value into bitcoin is a good place to put their value as compared with any other places that they might choose to put their value.