First i thought 100k is great, then i leave that in the market and will have enough for retirement.
Then i thought 400k is enough, with taking 4% per year i could actually finance my frugal lifestyle (16k per year = 11k after taxes),
then i thought better double that numbers with 800k (22k per year after taxes, 1800 per month, which is much more than i need for my frugal lifestyle).

Then i realized i better only take 3% per year, cause the 4% rule is for only 30 years, so better have 1mil (again 1800 per month)
Then i realized that with 1mil i basically live 'as rich' as a poor person who gets money from the government.

Then i went to look for houses in my small 300k random cheap city: it's 1mil at least.
Then you can calculate 2% per year of the cost of the house for: repairs, taxes, water, electricity, heating, garbage, insurance...) - so that's another 1mil for 50 years.
So that's 2mil. Then i need another 1mil to live for the rest of my life.
So 3mil just to have a normal ass house in the city.

Then i was thinking i would like to have a house with a big seminar room in the city that is easily reachable.
That's around 2mil. Another 2mil for all upkeep costs. Another 1mio for living.
So that's 5mil.
3mil for a house like that is more realistic,
so that's 7mil in total
Cutting it less close: 8mil.

Now, if you not just wanna have a house but change the world or smth, then i guess it becomes endless how much money you want.
If you want a great mansion, that's around 50 million, so you better have 100 million to also pay the upkeep. 

Funny how i thought 'wow, a millionaire, when you have a million you are rich' in former times.
Now as a millionaire you can have: a normal ass house not in the city for 700k, a 50k car and 250k stock portfolio.