It seems to be a 3 week cycle (or so) of special pricing with Albertsons & Vons (Safeway). Stater Bros does it too, however they sell select grade.
My local CAB grocery is getting very competitive also. $2.88/lb is kinda new - but I'm good for it.
I've found that after trimming one can add/estimate $2/lb to get the "real" price for trimmed Tri-Tip.