What do you mean? That if you use slavery to hurry production of a Legend Unit you'll get the unhappiness penalty as normal, or do you mean that Legends are more expensive to afford then a normal unit as the Wonder is more expensive to afford then a normal building? Maybe something else?
For the 2 proposals above, yes. You'll get +1 for a hurrying act as normal (with anything: buildings, units, wonders, national wonders, legends), and Legends being more expensive in then their normal unit counterpart are more expensive to buy (in my experience they normally are as expensive as national wonders).
If it's anything else I'm sorry I didn't understand, but I'm willing to help. Anyone who plays this awesome mod (my replacement for standard BtS for years now) deserves to know it better (I've been doing this with myself and some friends for some years already, we've finally taken it on Deity, but still no wins though only shameful losses).
I meant that in the sense that whiping a Wonder directly produces less Hammers per pop as whiping a normal item, leading to most people whiping something else with the intention of letting its overflow get into the wonder.
I know that feel bro, Standard BtS feels just unplayable now except for Multiplayer with this awesome mod.