in the States there are different prices as in Europe.
But a decent RZM dagger can be found for 450-500 euro in Europe.
As you stated already he has no knowledge of TR daggers, theirfore he thinks that every dagger is worth a fortune, even with removed insignia.
Some rules that can help a bit:
when buying RZM blades look for full crossgrain blades, undamaged grips and crossguard with as less as possible damage to the crossguard plating.
The chrome plating is their weak spot and eventually will come lose from the zinq or pot metal crossguards.
an eagle and a Sa button can be obtained for 80-100 euro, but keep in mind that the springs to attach them in the grip have to be bend inside the grip.
Thats not easy without the proper tools, otherwise you have to glue them in place, and thats not like you want it.
Better wait for a nice RZM dagger, save a bit more....... they are not that expensive.
even better, save evenmore and buy an early nickel one