On top of the Cornmarket wharges, the Dept. charges a "collection fee" of 1%, to compensate itself for all the difficulties, work, hassle etc in collecting the AVC contributions. If you opt for your own standalone PRSA AVC, you will also save yourself this additional 1%. As this is not a Cornmarket charge, it will NOT appear on any statement of fees & charges!! You'll need to factor it in.
On top of this, if you opt for the default fund, you will, if I recall correctly, be charged a 1.75% annual management fee. If, walking in off the street, you took out the same policy with Irish Life, you'd only be charged 1%.