I don’t think it’s the cost of reproducing the molds, It’s whether anyone would actually buy the sets, making the investment worthwhile
For instance, if Lego spent a lot of money developing a new Bionicle line, with new parts, new molds, etc and then it tanked, It would’ve been a waste of money that could’ve been spent making something more universal, like Ninjago’s 639th reboot or yet more Friends
And the only reason Bionicle was a thing in the first place was to save Lego from bankruptcy- They needed to try something different. Now, with as much money as they have, there’s no need to do anything different unless what they have isn’t making enough money
In case you hadn’t guessed already I don’t really know what i’m talking about here, i know nothing about business but anyway