Typically, that "Hz" number is in their special test room. The actual cuttoff can depend a lot on your room acoustics among other things. I would try to do a listening demo if you can. Play some source material you are quite familiar with, something with low bass.
In general, 2Hz difference probably would not be noticeable except to a few audiophiles. You still need to hear them for yourself though, if possible. If you can't hear the difference, then it won't matter which one you buy. If you can, then you will need to decide if the extra impact is worth the cost difference.
How much is the difference in cost? I have never heard of a dollar to Hz ratio, but I do know the sub I want to get retails for $2500 and is rated to 12Hz. Of course, I will try to find one used, because it is out of my price range, but it will match my other speakers, so I want it. I have heard this sub and compared it to others, and so far, I like it more than others I have heard. The fronts I have are rated down to 28Hz, so I definitely need a sub that goes lower than that.
Good luck with your search.