They are quoting you for a stainless steel best you can get at the moment insulated cylinder. €1200 to €1400 for a dual coil one sounds about right.
You can order a copper insulated 300 ltr cylinder from most plumbing merchants for less than 500. You save on the cylinder but when it comes to hot water pressure you end up buying the shower pumps which cancel out the savings. Best to stump up now for the stainless steel and have fully pressurised water at all taps.
Only problem with copper is that you need to have a vented hot water system unless you install a lot of safety devices.