Definitely. But I have also never ever argued for being able to take 30 abilities 
Nor do I generally talk very positively about D2 (and yes, the zero respec options in D2 was also bad).
This btw, is something I would be very positive about.
It is kinda a variant on my own cooldown based cost-proposals (heck, it once was part of my proposal, until I cut it to keep it more simple 
)
Something where it is really cheap to respec the first time you do it in a month, then a bit more expensive the next time. And ridiculously expensive, to the point that your computer is going to run out of memory, counting the currency cost, if you respec the 100th time in a month.
Such a system is definitely not the impression I got from Blizzards post. But yes, a scaling cost the more you do it in a month (or whatever timeframe) would be great.
That is true
But I dont think it means the game designers should just ignore what those 5% do. They should not cater to them, but it still seems worthwhile to either stop them, or make what they do, inefficient. So those 5% do not grow larger and larger.
It is up to a game dev to make sure that the most fun way to play is also the more rewarding.
But maybe more importantly, to make sure the worst ways to play, are not anywhere near the most rewarding. Because people will do all kind of crazy stuff to gain a 1% advantage.
And sure, I could choose not to care. But I do.