Your situation is a bit different than mine, because Hawaii has a mandated 30 day rabies quarantine. Normally, you wouldn t have to go through quarantine between locations within the US. I can tell you that the approximate one-week quarantine in Florida (for horses entering the country) the cost runs between $1500 - $3500. There is a daily board fee, but you also have to pay any vet expenses if the horse needs to be looked at for anything. Those are generally expensive and you are at the mercy of the facility.You should be able to choose from more than one certified quarantine facility. Do your research on what the options are. Not all quarantine facilities give the horses time outside of a small stall, so if it is going to be a 30-day stay, you might want to consider someplace where the horse will get some exercise.
Call shipping companies who have experience with live animals only. Talk to people who have animals in HI and see who they suggest and why. There are ALWAYS hidden fees.
FYI, I believe there s a max quarantine of 5 days.