Hi, I was formed at the University to design UML diagrams (class diagrams, sequence diagrams, activity diagrams, etc...). I have a degree in software engineering. The price you are asking for is too small. If you want quality work, it will deifnitely take at least 2 to 3 days. The price is negotiable, but I'll have to know how complex the system you want to describe is and what tool you want the diagrams to be designed with. I have experience with UML and can deliver quality.
If you are interested, please contact me (even if the price doesn't convince you).