additional processing and customs charges on goldring 1006 or nagaoka mp150

Absolutely no problem to mount any cartridge on your turntable/headshell since you will have a dedicated overhang gauge with your pioneer turntable for pioneer tonearm, it will take 5 minutes to set up your cart in the headshell correctly with that plastic overhang gauge. You don't need anything else and any special knowlenge. Custom charge depends on the custom regulation in your country. 

Thge better cartridges would be Ortofon M20 FL Super (under $200) or Fidelity-Research FR-5E  (under $150).

Another killer cartridge is Stanton 881s and 881s MKII from the 80s, read this article about it.   

LP gear sells both of those brands without those charges!
https://www.lpgear.com/

In my experience there are rarely any custom charges imposed in the US for personal items imported from abroad.

@yogiboy

LP gear sells both of those brands without those charges!

The charges are on the custom conrol on arrival, not by the shop on departure.

I’ve never heard about import tax in the USA, but there is always import tax in Europe for example. The shops just tying to say they are not responsible for any custom charges, that’s it.

I have bought stuff from Japan, China, Canada, Britain, Germany, Lithuania, Argentina, India ... without ANY custom charges! Regarding your TT: I too have a recently acquired Pioneer PLX1000. I use a Denon 103R mc cartridge on it. Way better than any MM cartridge! The PLX/Denon is competitive with multi-kilobuck gear!