Fair price. I'm on the verge of saying it's probably a little too low for those specs. You'd still probably sell that plan at 50GB HDD and 1GB RAM at $5/mo. What bandwidth do you plan on offering with that plan?
Best advice I can offer is do some market research. Look at what other company's are offering those specs at and work from that. Remember, you're just starting out providing the VPS service so competitive prices will bring in the clients providing you advertise in the right places.
I wish you luck