Dear Sir,
I have worked for the industry for many years including companies like Square-Enix and SEGA. I have done many works as level designer so I can make them progressive and with a learning curve as steep as you want.
I can't really tell you the cost because I don't know the interface you use to develop the levels, or if you just want a GDD with them. Please provide me with more details and take a look at my feedbacks.
Hugo