I bought Sennheiser IE80 8 yeas ago. They still work like absolutely new to this day, and they do sound better than any sub 50$ chi fi that I have ever heard. They have seen some abuse also, gym use with sweat, cycling use, commute, etc - absolutely like new after 8 years of torture, and they sound better.
I think now looking at these 8 years that 300$ was cheap as fk, even tho it was like half the salary at the time.