Yes I have, the best information and most current rates will be through Jet Pets in El Segundo , CA. The horse will likely be transported to a major center outside of Ireland to fill "pallets" being shipped from a diverse area in Europe to the west coast of the US.
Jet Pets is the only quarentine center available so regardless of carrier the horse will spend some time at that facility before being released to travel by van. The process can be less expensive if you import a gelding rather than a stallion or mare but having a knowledgeable agent is key to understanding the intangibles.
email Peden in Ireland - they are one of the best. Also whoever you are purchasing the horse from should be quite knowledgeable about shipping. It had gone down some but with the recent skyrocketing fuel prices am not sure what shipping will be. My horse was in quarantine for less than 24 hours - the shipper/agent called me when he arrived & let me know of his condition (a scrape on his tail) and said he be out as soon as lab work done. I thought it would be 2 days but it wasn't. Good luck w/ your Irish horse- I love mine!
I shipped from Germany but I highly recommend Guido Klatte. They did door-to-door arrangements for me and they will ship from Ireland. They all speak English quite well too, so no worries there. It cost just under 10K for my gelding from Germany to NY including quarantine. (this was a few months ago, and of course you're paying a lot of the fees in local currency (pound, euro, etc) so the exchange rate at the time also needs to be factored in. Feel free to PM me if you any additional questions.
A friend just imported a horse from Germany to CA, and if I remember correctly, geldings quarantine for several days at LAX and stallions and mares come up to UC Davis for quarantine for 2-3 weeks. Sorry, I have no idea how much it cost. Best of luck!