Well, the romans could push out a bridge with suprising efficiency. Ul'dah is a premodern society with a modern economy and industrial base. They would have no problem building a bridge like high bridge in under a year, so long as the money kept flowing.
This bridge in Spain was built by the romans in about two years:
https://en.wikipedia.org/wiki/Alc%C3%A1ntara_Bridge
It was at the edge of the empire though, so a place like highbridge, close to Ul'dah would likely be built more quickly.
This bridge in Spain was built by the romans in about two years:
https://en.wikipedia.org/wiki/Alc%C3%A1ntara_Bridge
It was at the edge of the empire though, so a place like highbridge, close to Ul'dah would likely be built more quickly.