Man you're gettin reamed, at
HostNuke (where we're hosted) they give you full access to PHP/MySQL and a CGI-Bin with SSH/FTP access, 5GB space and 30GB BW for as low as $7.95 (as high as $9.95)...
I wouldn't however host a site on your personal computer, I mean what if your ISP drops you offline for a while? what if you get popular and you have 0 internet connection? What if you want to use your connection while you have visitors? People shall crawl...
There are however, as previously stated, webhosts well cheaper than what you're flushing down the toilet...