If the only thing wrong with your computer is that the HDD is dead, I can't see that costing more than $200. Even including tax. Even if performed by Apple Certified Repair Persons*. Anyone quoting you more than that is probably trying to inflate their profit margins (or conservatively overestimating until you come in for an exam). You can get a computer
completely repaired by Apple after you spill half a bottle of '88 Cabernet Sauvignon onto the keyboard for that $800, and a hard drive requires only a
fraction of the labor and parts (and skill!) of such an undertaking.
Solid State Drives (SSDs) are still embarrassingly expensive, but if you insist on going SSD you can find some
pretty good deals at OWC on fast SSDs that won't decay in performance over time (this is a concern with SSDs). They also carry traditional mechanical HDDs which cost much, much less than SSDs while holding substantially more.
For people who want in-house backup but who desire fire-/flood-resistant storage, a company called
ioSafe has made a name for themselves by putting together some pretty durable external housings.
--Patrick
*I have my sources.