I don't think all of them can be right in that contest because allocating @Ricardo11 made a comment that is vague and somehow contradictory to what you said. He did not give conditions that will make someone who earns $2000 to invest 50% in Bitcoin like you try to give rather he is looking at the amount and not considering the responsibilities attached to the money. There are countries where monthly rent is as high as $500 which when removed from the $2000 will mean the investor will be left with $500 to cover for every other thing including food, transportation, medicine etc and is still expected to set aside emergency funds. How will it be possible to invest $50% under this condition?
I feel that the percentage will always vary per individual based on what we are comfortable with and what will give us the needed peace of mind that will not put us under any pressures to sell
Investing the entire amount remaining after meeting the requirements can be a fool's errand. Many have mentioned that it is possible to stop wastage and invest 50% of the income to meet the needs and 50% of the income. But I think there is currently no country where 50% of income can meet demand. Although possible, you cannot repeat it. You may invest once or twice with 50% of your income and the remaining 50% to meet your needs. Still you have to make more sacrifices. Investing One of the hallmarks of successful Bitcoin investing is investing with junk money. Which is to invest money that is left over from your income after meeting your normal needs and that you will not need in the future. Summary - No % matters in investing, rather invest with what you can afford. I don't think this matter should be argued further.