I've had them 4 times OP, and I love them, but they are a faff.
The most recent time, I had mine bright blue, so took them away from the salon, and dyed them myself, then they put them in.
From memory they were £400, for European cuticle correct hair.
I think it took around 4 hours to put them in, but I honestly can't remember.
You have to either put them in a high pony, or ideally pleat them each night before sleeping, and you can't let them air dry, you must use a low heat with the hairdryer (dry shampoo will become your new best friend). I also used to use the shower hose attachment, and only wash the top of my hair when I was in a rush.
You'll need to get a soft hairbrush too, so you don't pull the bonds out when you brush.
Mine got very matted, so took ages to take out, but I didn't look after mine as well as I should have.
My own hair wasn't damaged at all.