Hi,

What you are describing is the 'credit method' of eliminating double taxation. Which in layman terms allows you to deduct taxes paid in the other country from the taxes you have to pay in your own country. So example if you would pay 15% in your own country but you were taxed at 5% in the other country, makes you pay only 15-5=10% in your own country. If the 'credit method' were to be used in the above UAE example, what you said were true, you had to pay 15% in your home country, because 15-0=15.

However in the situation I described in the opening post the method used by the OECD model conventions is the 'exemption method'. Which means you only have to pay in the other country, whatever the percentage in that country is, and you are exempted entirely in your own country. So you are paying 0% in the UAE because they have no income tax on this, and you pay 0% in your home country, because the OECD convention uses the 'exemption method' in this case.

This is not a simple subject, but you can read more about it here: https://www.oecd.org/tax/treaties/1914467.pdf
Chapter V discusses methods of exemptions (these two).

About how affordable it is: Well the cheapest option I could find is renting a storage room and subletting it. I am told that costs around €1k/year with a provider that allows you to rent it out for profit.

It is a lot cheaper than renting the smallest condo in the cheapest area, those were around €1k/month and I haven't found one that is coming with a contract that allows subletting...

So for €1k you get to not pay any taxes on €90k worth of income. That sounds like a pretty good deal to me. You can also repeat the thing for family members so €90k/person/year for the cost of €1k/person/year. So you have about 1.1% cost. It is obviously worse if you only have for example €30k worth of crypto, but then you could team up with someone who is also willing to do the same thing...