NIFE are not for everyone, there are plenty of reasons why someone would want to give up on them. But If i was in the states, I would jump on them for that price!! The only concern I would have is their current voltage and that the voltage has never gone below 0.95v per cell. If the voltage currently is good then there may be a good chance they haven't gotten too low. What happens when the voltage droppes below 0.95v is the plates can delaminate as the metallurgy is different to what it was 80+ years ago.
Low voltage is the one thing that will potentially damage these cells, however you do bring the voltage under 0.95v to change out the electrolyte.