Is the Persian unique technology bugged?

I'm talking about the one that makes your archers cost no gold and replaces the cost with an additional wood cost. Archers normally cost 25 wood and 45 gold, so after the unique tech is researched, you would expect them to cost 70 wood. They instead cost only 50 wood. Is it supposed to be like that? The Malay unique tech that replaces the gold cost of militia with food works the way you would expect, with the militia units now costing 80 food (65 with supplies) instead of 60 food and 20 gold. Are the Persians supposed to get an additional 20 wood discount on their archers, or is that some sort of oversight? I can't be the only one who thinks that crossbowmen that only cost 50 wood can't be intended, right?