Yah, it probably should be in thre Mapping and scripting forum. I've moved it there.
Go to the Data\Balance folder and open the GameBalanceArtifact.txt file. Somewhere near the bottom you'll see this:
ARTEFACT_LASTLAND_HUNDRED_SOLDIERS 230000 1 1 1.1 9 0
ARTEFACT_LASTLAND_HUNDRED_ARCHERS 280000 1 1 1.1 9 0
ARTEFACT_LASTLAND_SIEGE_ENGINE 100000 1 1 1.1 9 0
The first number is the cost and the third number(I think) is the repeat. Set this at 0. For this file I think you might have to start a new game for it to take effect.