I have used both,k and non k chips and honestly think the savings is just there for those who just want a cheaper motherboard and aren't willing to overclock.
Saw no difference performance wise in the build i did earlier this year with the 2500k at stock,nor the 2500 non k i recently gifted to a family member.
Just a matter if someone wants to overclock,or save some coin and honestly i think it works out fine for the consumer this way as well.