If you are using LabVIEW with your PLC, or are substituting the paid SCADA from your PLC vendor for a LabVIEW based free SCADA, please see this video. SureView has its own library to use any PLC with NI LabVIEW.
Therefore, for a 1-time development cost/effort, you can get rid of the per-seat fee that is attracted, if you use a SCADA from any PLC vendor like Siemens, Allen-Bradley (AB), Mitsubishi, Schneider, ABB, Delta, Idec, Omron & so on. Thus you can have the massive power of LabVIEW in your PLC based systems as well as save on unit cost - at the same time!
You do not need any OPC server either! The library we have developed takes care of the interconnection between your PLC & LabVIEW.
Our company page of LabVIEW based SCADA for PLC based automation is here - https://sureview.xyz/plc-labview/