Also, keep in mind the TCO (Total Cost of Ownership).
If you decide to have your own servers/facility:
- Servers
- Replacement Spares
- Power (conditioning, redundancy, and protection)
- Fire Supression
- Backups
- Internet Feed (depending on how much you host, you may be looking at a fairly large pipe)
- Infratructure (cabling, routers, firewalls - cost depends on the outside connection)
- Insurance
- Facilities
- Legal Support (liability statements, contracts for clients, commerce laws by state)
- Merchant account for CC processing (now you're dealing with fraud and chargebacks)