I looked around to see how much water filter cartridges cost.  I found the Aquapure CBA5N cartiridge which costs $16.10; another Aquapure filter which is a little better cost $16.47.  The average eco-friendly Sigg water bottle cost 21.99.  If we are looking to see these bottles at the $20 range we are going to have to make our own filters from scratch and find cheaper stainless teal water bottles.  This project is now about developing the filter technology.