I'd say that it doesn't matter whether 10% of the field cashes or 30% of the field cashes....if you perform at a level that cashes higher than the field, you are in positive equity situation. If you also have the skills to run deep and maybe even win 1st or 2nd then your equity is even better.
I have a large enough sample size to know my stats are 18-22% cash rate for large MTTs. Since usually only 10% are paid, this means that I have roughly double the chance of cashing than the average entrant. still not a guarantee by any means, but clearly a positive expectation.
Now, I've heard it said a million times that tourney players "play for first" and this is true, But we don't look down on a min-cash...sure it didn't fulfill our main goal, but it is far from a failure. The way I look at a min cash is it pays for 2 more tries at getting first place.
But the main reason I play is honestly not for money. Tourney poker gives you so many different challenges and dynamics to work through, it is really everything that cash game decision making offers in terms of "entertainment" value except there are even more things to consider. In tourney it's a lot more than pot odds
, implied odds and bankroll management. There is stack size management, various bubbles to exploit, death traps to avoid, energy levels and tilt to consider (you can't just walk away), rising blinds to steal all very exciting and complex equations to balance. At any given time you have to ask yourself "What is my main goal right now" and the answer will often be very different than it would be at a cash table with the same hand and same opponent.
Then you add to that the fact that bigger "paydays" await tourney players combined with a softer field than cash and I can't really even be tempted to play cash games unless it's all I can find that will "scratch the itch"