OK here's my take on this iron head debacle. I myself, ported a set of X heads, bought all new Manley SS valves, Comp Beehive springs, Comp Retainers and locks, and seals. As well as, paying my machinist $300 to have new hardened exhaust seats installed, new bronze valve guides installed, cut the intake seats, and setup the valves and springs for my cam. In total I have around $1000 into my heads minus my time porting them.
A new set of bare Eddy's is about $1300. The reason I go bare is because you need to setup the springs for what your cam desires anyways and I don't like the valves that Eddy uses. Regardless of what anyone says, Eddy's still need to be checked out by a qualified machinist. You can never bolt a head on out of the box. When components are mass produced, the tolerances get skewed over time causing a lot of bad runs. Do a search on here about bad Eddy castings or machine work and you'll find a lot of unhappy people. So between the initial cost of the heads, components, and machine shop expense, You'll easily be in $1800 to $2000 for a set of properly setup Eddy's.
Another thing I want to address. I'm sure it's just a terminology issue, but there is no such thing as over scavenging. At low RPM's, with large exhaust ports and large tube headers, the velocity of the exhaust gases exiting the cylinder is low and doesn't create nearly any negative pressure in the cylinder before the piston starts on intake stroke. Higher RPM's allow for some of the intake charge to be pulled into the cylinder during valve overlap, before the piston starts its downward stroke in the cylinder. The more scavenging, the more air/fuel charge can be crammed into a cylinder. This directly relates to volumetric efficiency.
