Both Hawaii and Puerto Rico became United States territories in 1898, with Hawaii becoming the 50th and last State of our union in 1959, while Puerto Rico still remains a US territory. Hawaii is located in the middle of the Pacific Ocean, far away from the mainland. The closest US city to Honolulu is San Francisco, and yet that flight distance is 2082 miles. The closest major non-USA city from a different continent to Honolulu is Tokyo, Japan, and that flight distance is 3854 miles. In contrast, San Juan, Puerto Rico is 1031 miles away from Miami, Florida, and some 3,661 miles away from Lisbon, Portugal. Additionally, while Hawaii is literally in an ocean far away from any mainland, Puerto Rico is surrounded by many other islands in the Caribbean, as well as being close to Central America and South America. One would think, giving the location of Puerto Rico, that it would have little problem of being equal to or greater than Hawaii in regards to its income, but in fact, Hawaii according to the Census Bureau Median Family Income as reported by justice.gov tells us that for a "1 Earner Family Size", Hawaii has a median income of $53,751, whereas Puerto Rico comes in at a mere $23,168. This means that Puerto Rico's median family income is lower than any of the US fifty states, as well as being lower in median income than Guam, the Virgin Islands, and the Northern Mariana Islands (all US territories).
On the surface, this doesn't seem to make a whole lot of sense, Puerto Rico, in the sense of beauty, weather, and location, would appear to be the equal to or comparable to Hawaii, although this is obviously something that is relatively subjective. While, Hawaii and Puerto Rico are both tourist dependent, as well as being recipients of US military investment, Hawaii does have the all-important naval military base at Pearl Harbor, whereas Puerto Rico lacks this; but they are similar in their capabilities in regards to agriculture, pharmaceuticals, healthcare, and although Hawaii does have more graduates with Bachelor Degrees than Puerto Ricans, the disparity of 26.6% to 21.2%, while significant, is not substantial.
It is also possible too that Puerto Rico, suffers from a brain drain, to which ambitious Puerto Ricans leave the island, and move onto the mainland to search for their wealth and employment opportunities there, since native-born Puerto Ricans are considered to be United States citizens and hence have no barrier to entry. While that definitely makes sense, that doesn't answer the question as to why native Hawaiians' aren't too doing the very same thing.
Perhaps, finally, Hawaii is so much richer than Puerto Rico because Hawaii has attracted a large influx of foreign capital from places such as Japan, China, and Korea, to which each of these countries have people of enormous wealth that have a vested interest in seeing that some of their money is invested in American land and/or industry, and Hawaii is the closest United States state, with a population that is already heavily Asian and also easily accommodates such money. Puerto Rico, on the other hand, is probably considered to be just another Latin American country, having therefore more in common with Central and South American countries that were formerly colonized by Spain, and despite its status as a US territory of over one hundred years, making little progress in assimilating itself to America.