the problem for us is chrome is no longer chrome as many of us knew.
due to chromate being carconogeric (cancerous) there are many restrictions in the UK and Europe so you no longer get chrome, you get a nickle plate.
the Chinese still chrome but its a poor quality, the Indians still do but base metal quality is poor and chrome not much better.
I used to get mine done in Westinghouse (through the back door) only cost a few beers or fags as labour was paid by the company (doing other jobs or overtime). BUT to get a decent job nowadays its labour intensive. chrome plating involves a lot of polishing and the finish depends on the work underneath.
Ive used S&T at Yate and been happy, Ive known Doug Taylor at WSM visits a lot of shows, but I have known his work be suspect.
S&T did quote higher prices than new parts cost but they said, " you have the original parts", original quality but a lot of pitting that needed polishing out.
while there the next job was a Rolls Royce bumper, obviously money not a problem.
getting back to your tank, it would involve a lot of stripping and polishing and a big surface so price probably reflects the 7 layers that goes on, and work involved., even tough part of the tank chromw is covered by paint, they don't know so have to get the finish all over.
you might find a n Indian replacement tank with good chrome new for less, as they are copying a lot, they know there is a market. BUT , quality????
hope this helps.