Please help me out. I am thinking of making my first purchase of FOs. At NG the 16 oz. runs $14-$15, other places I see many of the same named FOs in the $20-$30 range. Plus if you buy five or more 16 oz bottles they discount $1 off each bottle. This makes thiers 40-50% less than the competitors. Is the concentration about the same? They recommend 5% which seems average.