Scott’s Cheap Fares reports airfares as low as $350 round-trip from Austin to Quito, Ecuador. Quito is one of the two gateways to the Galapagos Islands (the other is Guayaquil, Ecudaor). Several airlines from from Quito and Guayaquil to the Galapagos for reasonable airfares, or even airline frequent-flyer miles.
Check Google Flights for airfares on American Airlines, Delta, JetBlue and United.
Last month I flew American Airlines from Austin to Guayaquil for 17,500 frequent-flyer miles in Economy. Airfare for a flight on LATAM from Guayaquil to the major Galapagos airport was about $200. The entire trip back, from Galapagos to Austin, was just 30,000 AA miles in First Class.
You do not need to spend a lot of money to see the Galapagos. During my 5 nights there, I spent less than $1000 for hotels+tours+dining.