Yes, glass recycling is effective in terms of the glass is already made, and energy does not need to be expended to create it from scratch. What is ineffective is the current system of recycling glass. If someone could come up with a better system, then it would be cost effective right now and not just in the long run.
Recycling glass is cost effective because it costs less to recycle old glass than it does to find and make new glass. This is a simple matter of economics and can not really be debated. Not only is it cost effective but it is important for our enviromental health to recycle glass.
Glass recycling is cost effective because of its positive impact on the environment. Sure, there is a cost involved with recycling, but I believe that there is a higher cost to pay if we don't participate in this and continue to harm our planet. Investing in our planet is a worthwhile venture.
With quartz (sand) being one of the easiest-to-access minerals in the earth's crust, and with it being cheap to melt and shape, it's more cost effective to use raw materials. Once heated and formed, perhaps with paper labels or color or other materials added, the glass needs sorting and special handling before it can be used. It's cheaper to throw the glass away and let Mother Nature reclaim the quartz.