The truth is somewhere in the middle. You may don't need to have 17.000€ to play a 170€ tourney. But, if 170€ is your whole bankroll then playing that in a single tournament is foolish.
In your situation you say, "Hey since I can get a pay check next month if I have 170€ to enter a tournament, that means I have 170€ to enter a tourney! But.. Doing that thing every month for a year, means you have a yearly bankroll of 2.000€ for poker. If 170€ was all you had for that year, playing in a 170€ tournament buyin is not your best decision. That's the reason people talking about minimum buyins.
Now let me tell you an example, you play in that 170€ tourney and you win 1.000€. So now you can enter a 1.000€ tourney? You surely can, but if you do that, it is guaranteed that sooner or later you will end with zero profit or below.
Now, in your defence, Negreanu thought the same thing when started playing poker. He made the calculations and saw that to be able to have the minimum buyins for the games he wanted to play, it would take him decades. So he took the short path. But its Negreanu we are talking about.
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