Teva can see a $250m/yr [Lovenox] product if they get approval. That means it would be worthwhile for them to spend $500m to get it approved. I have to believe that given Teva's overall resources, $500m and the FDA roadmap can achieve approval.
Time is also a factor; indeed, for a company as affluent as Teva, time is the main factor, IMO.
If Teva were to start from scratch, which is what I believe they would have to do to produce a serious Lovenox candidate for the US market, it would likely be 2016 or later before they could have a marketed product—if they could even do it at all. When you discount the potential cash flows back to the present and adjust them for the probability of failure, the economic impetus for the project is not nearly as compelling as you make it seem.
“The efficient-market hypothesis may be the foremost piece of B.S. ever promulgated in any area of human knowledge!”