My accountant charged me €600 +VAT the past few years,.. EVERY year she saved me more than she charged me.
For me though the main advantage is peace of mind and reduction in stress. When an accountant does it you know its done right, and its done quick. When I tried to do it myself the first year I spent weeks reading books, online guides, the revenue website, attempting to fill out forms and getting more & more stressed every day. When I finally relented & took my books to a professional I found I'd done loads wrong! She fixed my mistakes & claimed back loads I didn't know I could.