Make the Call states you have to pay the PRINTED cost of an ally. Also, iirc, Quinjet specifically states it is used against the PRINTED cost of the ally

Does this mean Make the Call and Quinjet cannot be used in conjunction with cards like Avengers Tower or Steve Rogers' ability to reduce ally costs?

Yes, I don’t think those discounts would interact. You aren’t playing an ally with Make the call or Quinjet (you put them into play) so you don’t get the discount to the first ally you play when you use them.

And it also doesn't count against Steve Rogers' ability for that same reason. "Play" and "put into play" are mutually exclusive ways for cards to enter play.

In the livestream, the designer playing Cap (I forget which one) did a play where he used a Make the Call, then immediately after played a different Ally with his discount, because the other one wasn't 'played'.

But you can use Power of Leadership on a Leadership ally with MtC, correct?

6 minutes ago, Rogue 4 said:

But you can use Power of Leadership on a Leadership ally with MtC, correct?

Yep, they’ve verbally confirmed that on stream I believe.