For orchid $5 note, it must have Goh Keng Swee's signature one
to be so valuable that it is worth $500. But must be in good
condition like EF and above, preferrably graded by PCGS.
For orchid $1 (and $5 if it is non-GKS signature one), unless it
has golden serial number or mint error, very hard to sell at such
price.