Hm I get what you mean but no, I think the only thing cheaper is the panel itself as theyre way cheaper than full spectrum. I mean yes you will need slightly less wattage if you use only blue because blue and red are the 2 essential colors but I dont think its worth it as to what youre saving compared to what youre losing in performance. Bluerples gave me more stretched plants, always, more internodal space and less bushyness than full spectrum, thats why I dont use them anymore and almost nobody does as you can see in the forum. The usual LED brands for weed wont sell you a blurple either. That said if you have a full spectrum and you wanna add some blue because your panel lacks some blue for veg and then you wanna reinforce with more red diodes in flower thats not a bad idea but without losing the full spectrum from whites.