There is nothing wrong with the Flourish line. They are all good sources of nutrients. Don't forget that it's not just fertilizers you will be switching. The amount you dose now will be increased SIGNIFICANTLY when using the EI method. You think Seachem Flourish line is expensive now? Try to use it dosing EI levels.
I made a few calculations to compare prices. The mixtures are comparable to each other.
KNO3 1LB $3.00 makes 6.3 liters of Flourish Nitrogen.
6.250 liters of Flourish nitrogen costs $87
KH2PO4 1LB $5.00 makes 10.5 liters of Flourish Phosphorus.
10.5 liters of Flourish Phosphorus costs $144.94
K2SO4 1LB $3.00 makes 3.25 liters of Flourish Potassium.
3.25 liters of Flourish Potassium costs $83.30
Plantex 1 LB $12.00 makes 9.25 liters of Flourish comprehensive.
3.25 liters of Flourish Comprehensive costs $137.38
Grand total: $23 versus $452.62
5% the cost of Seachem's line
The dry fertilizer prices are from NilOCG and the Flourish prices are from Doctors Foster and Smith.