According to wikipedia Guam has a GDP per capita of $30,500 and American Samoa has an even lower GDP per capita of $13,000 so 5:1 is closer to reality for the US.

That said. The US is not the only country to oficially use the US dollar. Among others, Ecuador has a GDP per capita of just under $12,000 and uses the US dollar, Palau $16,000, East Timor $5,500, and lowest are Marshall Islands and Micronesia both with GDP per capita under $4,000 bringing the ratio closer to 1:18.

Also there are plenty of counties with even lower GDP that uses the dollar unofficially, so I don’t see a problem with a high GDP per capita ratio.

Edit: Equatorial Guinea is also an outlier with high GDP and low population. We could arbitrarily decide to include San Francisco in the US example with a GDP per person of over $100,000 bringing the US ratio up to 1:7 and the US dollar ratio to 1:25