I purchased a 5 gallon box of the NERL Reagent Grade Water for $33 including shipping. The supplier I bought from (MedicalMailOrder.com) no longer carries the water, but if you're willing to go for a 5 gal. quantity it can be found much much cheaper than $30/gallon. The box includes a spigot and is easy to use in refilling a dispenser bottle.
I did a quick google and found this: NERL 9805. It is not identical to their Reagent Grade product (9800-5), but very close. Compare the products at Thermo Scientific.
You may be able to find either for less money with a bit more searching.
As always, the Audiogon search is your friend. Read for more answers to your question.
Tim