If the flag isn't set, it doesn't bother any default NPC.
Flag
1 = Disable Discount
2 = Disable Overcharge
Examples
Discount & Overcharge are disabled here
prontera,147,167,6 shop Shop 1 872,2102:-1,2104:-1,501:-1,3
Overcharge is disabled
prontera,147,164,6 shop Shop 2 872,2102:-1,2104:-1,501:-1,2
Discount is disabled
prontera,147,161,6 shop Shop 3 872,2102:-1,2104:-1,501:-1,1
When file is loaded with that flag, you will get this Info
Screenshot_30.png
Download
Ahh sorry, from now, I think I just throw my modification on my fork (under PServeRO account), it'll easier for me to update some mode later.
https://github.com/pservero/rathena/compare/custom/shop_flag
Diff: https://github.com/pservero/rathena/compare/custom/shop_flag.diff
Cyd, can you also release for eA? please