I like Noodler's/Swisher's ink quite a lot, and I appreciate paying for
ink and not a fancy bottle, but I have decided to get some bottles to
decant the 'colored water' of my choice into. Partly this comes from
having trouble seeing how far I am dipping the pen into the ink and
getting it down too far and having to wipe out the cap threads (or
drain out the cavity around the cap clip on my Lamy 2000s) but also
from having knocked a capped, full bottle of American Eel off of my
desk onto a brand new hardwood floor. Of course, the cap broke and I
can now tell you from hands on experience that Nathan is not kidding
about amazing dye concentration.
At any rate it seems that retailers can't profitably stock bottles in
the quantities involved. Thinking back on some derogatory comments on
a brand of ink I found a place that sells Montblanc ink cheap.
Shoplet.com:

http://www.shoplet.com/office/db/MNB12569.html

has Montblanc ink for $6.62 each, with free shipping over $25 which is
covered by four bottles. They really are good bottles.