For those that love Retayne and Synthropol....have you considered buying it by the gallon? I have purchased from Colorado Wholesale Dyes by the gallon these products. (Disclousure: I'm in no way affliated with this company, my research background I always search for the most inexpensive way to purchase products I like)
I just called and the current price for a gallon of either product is $19.99. Of course there is shipping to be added, but if you buy the 8oz bottles at your LQS they can run anywhere from $8-12 per 8 oz bottle.
Colorado Wholesale Dyes phone number is: 1-800-697-1566. For those living in the Denver metro area they are in Littleton and you can pick it up. My experience is with them outstanding.