I run about the same mileage, and feel your pain about the expense of a jogging stroller. However, I would caution you about buying a cheap one - I have found that with jogging strollers, higher quality does equal higher cost. I have a BOB,which was about 400, but we will use it for years - and I wish I had bought it before my son was born, instead of at 3 months when we already have a Chicco travel system stroller. The infant insert works great with your infant carrier :) I have not used my Chicco travel system stroller that came with our car seat once since we bought the BOB.
If you are looking for something cheaper, I would suggest looking on craigslist for someone selling a BOB. Baby Trend does sell some cheaper, but many of the "jogging strollers" you see out there aren't truly meant for jogging, they are just more all terrain type strollers. I know that doesn't help your question much, but be on the lookout for sales/deals - you'll find something.