I purchases a 225 gallon bucket for $55. I don't think that's a bad price for 225 gallons for a good salt mix. Every batch has it's own individual stats. Mine for copper was ... 0.0030.
I'm usee to Oceanic Natural Sea Salt Mix which really isn't meant for reef tanks. So I made the switch. Comparing the two, Oceanic does dissolve really fast, but you always have to adjust the water before you put it in your tank (pH, Ca and Ak).
With Salinity I didn't have to adjust anything which was a nice change of pace. Salinity does take longer to dissolve, but only minutes longer. So far I like it a lot better. I'll keep you posted with water changes and see if there's a long term difference.