It's simple, Disney keeps raising prices because it increases their profits. If, at some point, they make less profits from a price increase, they will halt it. As for people talking about prices 5-7 years ago. Keep in mind, back then, the U.S. was just coming off the Great Recession. Also,
DCL was not nearly as popular as it is now. Also, not every calculation is perfect. Some sailings, they may have miscalculated the pricing and have to run specials (e.g., guaranteed rates, etc.) If people aren't thinking of leaving Disney, then that tells Disney they are not increasing the price enough.