Mr.Fishy

So I use bazzar.tf and I see stranges crafted with strange parts and they say these prices that seem a bit high compared to what the person is buying for so I stay away from them so I don't screw myself up and make a bad trade for me but I want to understand how do I know if it's showing the right price I've tried to use backpack to get a price but I never can so if someone could help me understand this that would be very nice.

Thank you I just wasn't sure now I can focus on other things

So I have a festiviser (sorry if I spelled that wrong) I'm wondering if you can get a strange festive flame thrower by buying a strange flame thrower and festivising it. I've searched so much to find the answer. I don't want to buy the strange flame thrower if I can't festivise it. So someone plz help me I want to get into trading and I saw this opportunity but I don't know all the info needed