Official http://goldback.com exchange rate for 09/13/2023 remains $4.04, unchanged from 09/12/2023.
After a review of online sellers' prices, the best price for an in-stock 1 Goldback is $3.68 over at Defy The Grid
https://defythegrid.com/product-category/gold/aurum/goldbacks
Best price for a 100 pack of 1GB is $363.29 at Oz Bullion
https://ozbullion.com/products/nevada-goldback-1-note-aurum-100-pack-24k-gold-bills-random-year
The best price for an in-stock 50 Goldback is $176.05 at APMEX