There used to be a time when every part relating to Assault was made out of solid gold. Trends come and go.
While Paperboy panels are very rare loose, there also can't be that many cabinets missing them in the first place, it isn't like Paperboys ever got converted to anything else. People are sitting on spare panels already, those will come to market and drive the price down. The actual real need for paperboy panels (not for spares or upgrades, but actual cabinets missing panels), is probably less than 20 worldwide.