Hi Dave, I'm originally from Guam and fly back often so I've learned of a lot of ways to getting cheap flights to Micronesia. $2,000 is crazy from the East Coast. All flights to Palau and Yap, must stop by Guam first. Its an island hopper thing, You'll go from whereever in the east coast, to LA probably, then to Honolulu, then to Guam, then to Yap (flights to Palau stop in Yap), then to Palau. You want to to find a travel agent that is a "consolidator", meaning they buy bulk tickets from continental wholesale and sell it to the public with low profit margins (they make it up on the amount of tickets they sell). One consolidator I know is in Glendale, CA, its called "travelmate", it might be also listed as rock bottom airfares or something like that. Another one is airticketmasters.com, its better to call them though. I flew back in January and got my ticket for about $1,350 which included Guam and Yap. It might be cheaper to book your east coast to west coast tickets separtately through southwest or jetblue or through some specials.
Alternately, you could fly into LA or San Francisco however, then book a ticket to Guam through Asiana airlines for really cheap, like $800900(sometimes as low as $650). However, there is a 14 hour layover in Korea, but its not too bad, you get there early morning, tour the city, shop or whatever for the day, then head back to the airport in the evening for the Guam flight. For the Asiana ticket, a good consolidator is Mike Lee Travel in Oakland, CA. Then you could book your yap and palau island hopper flights through Continental. I recommend you do that with the consolidators I mentioned, or sometimes Continental on Guam will have good package prices to Yap and Palau, you can call them at 671-647-MIKE(as in air micronesia). You can get all the phone numbers for the consolidators by calling the operators in each city. 510-555-1212 for Oakland, and 626-555-1212 for Glendale.
Yap was a lot of fun... even if there were no mantas, the diving there was excellent, the coral and marine life was really healthy and unspoiled. The mantas were great, we saw them everytime we dove Mi'il channel and they swam about 2 feet above your head. Check out my Yap trip report a few postings down for more info on dive shops and hotels in Yap.
Have fun and good luck!