I paid about $175 for the ABA set new then installed all the ERR components myself, so no labor involved. I had the set for about 7 years before I converted it. The $200 to convert it was cheaper than buying a already command control set, even after selling the Williams units, so that's why I upgraded them.
I figured that the upgrade was along the lines of spending $25k to restore a car that's worth $8k. Even though you spent $25k you still have a car that's worth only $8k.