Visiting the Galapagos is not cheap, owing to travel restrictions and the remote nature of the archipelago. The only way to get in the islands from the main land is by plane from Guayaquil or Quito airports. Flights travel to the Galapagos in the morning and return in the afternoon, typically requiring a forced overnight on the continent in each direction.
By plane
Flights to the Galapagos are relatively easy to arrange and depart from Quito and Guayaquil on a daily basis for the Isla Baltra Airport, about two hours by public transport from Puerto Ayora, the main settlement of the Galapagos, on the central island of Santa Cruz.There are also daily flights to San Cristóbal. The airport is a 20 minute walk from the center of Puerto Baquerizo Moreno.
Flights from Guayaquil are slightly less expensive than from Quito, however as there is more availability from Quito as there are typically 2 flights a day from Quito and only 1 from Guayaquil. Most flights from Quito route through Guayaquil.
Aerogal (http://www.aerogal.com.ec/), Tame (http://www.tame.com.ec) and LAN Airlines (http://www.LAN.com) have flights to the Galapagos. The price varies a bit between companies, for foreigners around $457 from Quito in low season / $505-$512 in high season July, August and December and less from Guayaquil, $419 low season to $522 in high season. Eucadorians pay almost half the price and there is a 15% discount on TAME flights and a 20% discount on Aerogal flights if you have an ISIC studentcard.
It's not possible to buy a one way ticket without proof of transportation from the islands. It's easy however to change the date of your return ticket or to switch your departure to another island.
Inter-island flights are available to both major airports Baltra and San Cristobal for flights between islands. There is also a small airport in Isabela. Flights usually range $160-$170 each way or $260 round trip.
By ship
Private yachts can arrive into any of the 5 ports in Galapagos while in transit and remain at that port for a maximum of 21 days. Boats wishing to visit more than one site or cruise the islands may do so but only by special permit from the national park and by working with a licensed yacht agency.
There are cargo boats that travel to the Galapagos each week. However these boats are not allowed to take travelers on board.