For how long was BTC above 10k? The average price since 2017 probably was about 5-7k.
There were months when it was 3200, such as December. That would be like 500 USD. (What would be rent and health plan only probably). There is no public health plan here (there is but you will die if you need it.)
Also, can you live without ever paying taxes?
If you have a child, forget about all that math lol
Signatures, bounties are a great complementary income. They are very significant anywhere in the world, but I wouldn't live solely with them. Don't think it is safe or wise.
I do not know how then people live in Brazil with average of $500 per month if you need up to $2000 to live some decent life...I know what you consider decent life, but you are talking about houses, travelling, eating in restaurants and we are not on same page here. You are also wrong about comparing London&Rio de Janeiro, how cost of life can be same in those two cities? I check prices and most of things are 50% cheaper in Rio, then in London - and I can not live in London with $1500 because it is one of the most expensive cities in the world - they will be soon out of EU.
Let's say I bought 5 BTC back in 2015 for total of $1000, and I sell them for $100k in 2017, and then I invest half to buy 15+ Bitcoins this year at price of $3000 - Now I have $50k and 15 BTC, all from $1000 investment. This is just example, but it show that if people are smart, they can make big money with small investment.
I agree that signature campaign should not be primary job, but who are you or me to to judge others people lives - If OP wants to live such life it is his choice, and maybe he will profit more in 10 years in front of his PC then to work on some regular job all of his life.