Mathematically it is true, with two caveats. If you regularly place in the # 1 spot for events or if you are more ungodly lucky on drops than anyone I have ever heard of.
To level 1 5 star requires 1 dblade and 1 tome. Those drop once every 10 weeks or so on a rare quest. From there the math is easy, you can do 5 a year from those and you may get lucky enough to do a 6th from drops. To do 12 a year is 2x that. hence you are buying mats.
And this is backed up by the handful of people I know that do this, they all admit to buying many of the offers that have dblades and tomes.