Thanks for writing in.
I read your query,I would like to inform you that price of invisalign
is more that traditional braces.
It ranges between 3000$-9000$,depends on practitioner.
So i will suggest you now there is no point of negotiation because treatment has been started and you can ask for retainers after your treatment including in this cost,but you can only try.
Dr. Gunjan Gupta