Thai Airways will quote you a fare of £625 from Dublin to Denpasar. Singapore Airlines' fare is £770. The Thai flight leaves London Heathrow daily at 11:50 a.m. and takes 17 hours 55 minutes, with a stop in Bangkok.
Prices in Bali fluctuate rather a lot as the Indonesian rupiah goes up and down. Recently it has been low, 5000 to the Irish pound