Please keep in mind that the amount needed for your tank won't be the amount needed for another tank. Fert dosing is dependent upon plant mass, lighting used, CO2 presence.
Just found a combination fert that is cheaper than $15. Heard about it at Atlanta Aquarium Association meeting. A single container is $10 + $6 for shipping. You mix 1.5 tsp. with 1 gallon of water. Then dose 5ml every other week. It last a long time. Thus perhaps could partner with someone.