When I moved in to my new house I accidentally broke the existing screen door. I bought and installed a new storm door myself.
If you're willing to roll with some curveballs (for me, the exterior door moulding had to be cut back) you can install your own storm door in an afternoon. Ours cost about $200. Front doors are more expensive, but easier to install as the hinges usually match up pretty well with what's already there.