How often can you get that week off? Most people I know working in the service industry have to fight to get that even once a year. Hopefully someone's OK not going home and seeing their family in a year to take a vacation like this. Hopefully they don't get sick and need the week for that.
To the cost: $6500 for two is low. Just getting there will be a significant amount, especially if you don't live in a major travel hub like LA or NYC.
"My Galapagos excursion took place on a boat with over a dozen other travelers."
Most ships are significantly more than $4000 per person, not including travel to the area: https://www.galapagosislands.com/cruises/ship
The absolute cheapest is the 100-passsenger Galapagos Legend at $2000 per person for 4 days, 3 nights - but a flight to Baltra Airport from, say, Pittsburgh will add another $1800 per person, and even from Chicago it's $1500 on a mix of airlines.
If you want a small ship with only a dozen others it will be significantly more expensive. If you want a week on something of that size you're looking at $4700 per person and up - plus travel. https://www.galapagosislands.com/cruises/catamaran/tiptop-ii