I think you should get more money when you sell emeralds to /shop because 30Nbz really shouldn't be enough for how rare they are something like 100Nbz and 110Nbz(for VIPs)
And for the ores 120Nbz and 125Nbz(for VIPs)
I agree, but it will be tough, players like tidal for example had an emerald island in 2014, and many ppl have loads of emeralds from those custom biomes in town. Going from 30 to 100 for example is a big jump, it' would be worth it then to empty out shops on the server who let you buy it from them for 50 or 75 and then sell for 110 with vip+
It's tough after four years to unbalance that sorta stuff.
I wish we could use emerald blocks for example to have as an effect, like if you have a path and you place them that when you walk over them you can get a speed boost for a few seconds. Might make town travel a bit more fun