ADI is doing the effects for AVP2, and they may still have a lot of the Props that were used for AVP functional. They could be stored in a Wherehouse.
At least the molds for the Aliens. They could use the old molds, and make some minor changes, without having to re-do the whole things.
Take the dome off the head, which may just simply un-clip any how for example.
The Animatronic Queen did have a non-battle damaged head as well, so IF there is a Queen in the movie, even just for one small scene, they could just use the Prop that was used in AVP.
Heck, they may even get away with using the 1/3rd scale Queen if she never gets a chance to leave the nest and gets blown up beforehand. They could easily do this as long as there are no humans, or anything else in the scene with her to give away the 1/3rd scale.
We would still have a lot of battles in the Town with Adult Aliens, including the showdown with the PredAlien.
The Pred costume may have to be re-made as it is not going to be overly muscular like in the first one, but they may have some reference material from previous films to cast from. Either way this should not cost too much. The could probably alter existing equipment to fit it, and customize it, and change colors with a new paint job etc... none of which should run too much cash.
The PredAlien would be the only new creature that HAS built from scratch. I think it should be bigger than a human-bred Alien, but still smaller than the Queen, so the PredAlien will not have to be gigantic. I was thinking about 10ft tall when standing errect, whereas the Queen is 16ft when hunched over like a T-Rex.
The Pred-Alien may be less expensive to build from scratch than would be a new Queen.
So there you go with the effects.
New Pred bodysuit.
Build the Predalien.
Everything else can be slightly altered pieces from existing Props.
I think those methods may be in use to save money.
Someone correct me if I'm wrong and this would in fact cost more.