1) A fraction? Well it depends.
If you're looking for a high end cluster (1 Server for web, another for database, another for application, etc.) thats a good $2,000 - $3,000
If you're thinking even smaller than that (1 server for everything) then a Dual Quad Core Xeon Server would cost you $1000 - $2000.
2) In a datacenter with multiple high-end bandwidth providers that have redundant power and UPS with an expensive fire suppression system and security cameras with hand readers around every corner along with thousands of pounds of air-conditioned air pumped into their facility which house thousands of servers and real live tech guys.
If you meant more on what the server is running and not literally the 'environment' the server is in, then use Linux running Apache with PHP + MySQL.
3) If it's media things you're hosting, your best bet is with
http://rackspace.com/ - On the expensive side, but they're really good with server resource intensive sites. (Focus more on mission-critical websites that require clusters rather than selling single servers, however single servers are still available.)
http://liquidweb.com/ - Owns two of their own datacenters in central US. Great tech support.
http://steadfast.net/ - Owns their own datacenter in Chicago. No personal experience with them, but seem more professional and more promising.
http://softlayer.com/ - Unsure whether they own their own datacenter, but they also seem very promising. Commonly used with webhosts.