Costco sells my favorite yoga tights ("Tuff Athletics" brand) for about $17. They are good quality, opaque, wash great, come in many colors, and are nicer than Lululemon pants---because I get the keep the $75 difference in price! They fit true to size and don't sag.
I treated myself to a new pair for my upcoming trip to London to wear as leggings. Tuff has added a flat drawstring and a very discrete zippered pocket at the waistband. It is large enough for a credit card and some cash and will be a great place to hide money belt type items, but just a tad too small for a passport. Believe me, no pick-pocketer is going to access my leggings!