That is probably an figure inflated by opponents to use as a scare tactic
You do realise that in order to make Elblag even remotely viable as a seaport, they would have to do almost total renovation of the port (including a huge amount of dredging), rebuild a railway bridge, build some locks and build the canal. It would be expensive, expensive work.
Smaller figures have also been mentioned.
By people who have no idea what large projects cost.
Ain't there no such thing in Poland as muncipal bonds?
No. No-one would trust the municipality to actually spend the money on what it's supposed to be spent on.