It's dollars per foot, yes. Honestly though, since they are all in the same relative scale, and the point is what was cheaper and by what percent, this feels like pedantry.

Put another way - outside of being technically correct, why does it matter to the point at hand?

I pay about $350 per kilometer for 24 count flat all dielectric G.657A1 fibre with 2 x 2.0mm fibreglass strength members. Add about $100 for shipping from overseas.