material:
4 8ft sections of 6ft picket fence; $120. 6 8ft post, $70; 1 metal gate + hardware, $50. 6 bags of concrete, $20. Misc. supplies, $15.
Total: <300.
Labor: 2 people, <1day, $150.
If you want to do it yourself, the hardest part is to dig the holes. So get a hole digging tool. With an occasional(to lift and hold the 8ft sections) help you can do it in less than a day.