Personally I am under the impression that Guzma will see a spike in price after they stop printing Burning Shadows, and will only start to dip once it is near rotation. That is also most likely why all of the other cards such as Brigette and Sycamore are less expensive, as they will most likely (definitely) rotate out. I think that Guzma will actually go up to somewhere around $65 before going down, since it is really really the best thing we have now. Same as Cynthia. She will more than likely start high and continue to be high, because from my understanding, it is very possible that Cynthia can come as a holo instead of an uncommon, and since it is the only aggressive draw supporter we will have after rotation, it will, by my prediction, be akin to Shaymin-EX or the current Tapu Lele-GX in terms of price. I don't have an economics degree, but I think I have a decent understanding of what the meta will want, and it's Cynthia.This is because, people who want the FAs, already bought them.
Now, they've lowered it, so they can sell to the people who were hesitant about the high price.
People still want Guzma FAs, so it's still a high price, but not as high as it once was.
Cynthia's price will be dependent on what people are willing to pay for it.
There are rare cases, where the love for a card/character can keep the price high, as people consistently buy it at that price; not sure if that will be the case here though.
It will likely start around $45-50, and drop overtime to about $25, once all the fanatics have bought their copy.