Currently i am a hosting provider myself, but host some of my own projects on the server. One of the projects was to test a PHP app we programmed, it worked obviously, as 2 months later this project turns out to be succesfull. 2500 members in 3 months, and 25000 downloads a month later we decided to look into selling it as this is getting way too big.
The downloads are small textfiles used for subtitling divx files. Mainly downloaded for foreign DVD backups or hearing impared.
All under 30 KB and currently about 1000 files. (and growing) The site fills about 50 mb of space in total.
In july it pulled about +10 Gigs of bandwidth.
It had 1195 unique visitors a day and growing.
Monthly total unique visitors: 34656 and 6873801 requests or hits.
Probably around $500-1200 depending on your marketing skills. I recentely sold a gaming site that recieved an average of 11,000 unique hits per day (19,000 high) and 6.7 million page views per month for $3,000 US... probably could have gotten more, but the market is down right now. Anyways, hopefully that will give you an idea of what sites sell for... I think the question any buyer will ask himself is "How can this site make me money?". So when selling the site, be sure to mention possible ways that an owner could make money off of it.