JR Peter's Jacks Nutrients.
Jacks Part A 5-12-26 (Hydro, includes trace elements)
Cal-Nitrate 15-0-0
Epsom salt - magnesium and sulfur
if you buy in bulk, it'll be a bit less that $0.04 per gallon. It'll work in DWC and coco. I've used it in soil successfully too, but made for soilless (coco, peat, hydroton etc) and hydro.
there's another brand that has a very similar 3-part system. Same price point. if same ingredients, same thing, but not sure off the top of my head. only mention due to availability concerns. Anything similar will be a great product to use.