So in the Speechcraft tree we have the perk "Allure" that will give you a buy/sell bonus from the opposite six.

Now could this perk also work like the Lady Killer perk in FO3, where it unlocks special dialogs to charm the opposite six into doing something?

No, it gives you a buy/sell bonus from the opposite six.

Combined with the other discount perks, you can get up to 60% off. That's an insane discount. I'm going to max out the speech perk tree anyway, but I may go with it first. It seems like it's more useful to get early in the game.

Yep, a bit too much. 30%, I would understand but 60? Way too much? Ah, well... I don't think anyone will spend so many perks in speechcraft.

As long as the 60% discount still keeps us paying atleast 120% of an items value and selling of at most 80% I'm happy. The bigger the speechcraft discount the better, it only means difficulty is greater without speechcraft (assuming they are keeping reasonable soft caps).

I'm hoping we pay 180% without perks and sell for 20% without perks. More likely they put in hard caps though so at a certain point the perks just dont do anything for certain vendors.