I tried the free Internet access inside customs at the Perth International Airport near the food area. At the end of the session I hit the return button to delete private data and the machine rebooted. The operating system was Ubuntu 9.04.
Think of the low cost of providing a service like that. One phone line at AU$132 per year. A medium ADSL2+ connection is $40 per month or $480 per year. The ADSL+ modem is $70 with a free splitter. A reliable 8 port switch is is $60.
Each computer is about $599 retail but buying them in a bunch, you would leave out the DVD drive, leave out Windows, and negotiate a decent discount bringing the price below $500 each. Assume 4 computers at a cost of $2000.
The total is $2742 in the first year then just $51 per month after that. In a cafe you could charge $2 per hour for access or ask people to buy a coffee for each 30 minutes of usage and make $6 profit on the coffee each hour. More people would stay longer then buy food with $2 profit per extra sandwich or cake. At the airport you are making $4 profit per food item and need just one extra item per person per hour to return a big profit. Assume 4 people using the 4 computers. Assume one food item per person per hour (At perth they forgot to advertise food near the computers) and 6 hours of peak traffic before breakfast, lunch, and dinner time flights. 24 people hours by $4 is nearly $100 per day by 7 days per week paying for the system in the first month.
Yeah there is a furniture cost but there is a furniture cost for cafe seats and people are more likely to stay with something to do. Mice break and you can buy good mice for $12, less than 1 hour of trade. Screens break but not often. Avoid no name brands and the cheaper end of Dell, etc. Look for a supplier with a decent on 3 year site guarantee but not a premium same day guarantee.
You could order a computer with a Compact Flash card as the boot disk and configure all temporary and page files into a RAM disk. You reduce the price, noise, and electricity use. Some manufacturers have tiny preconfigured diskless boxes for this type of use.
The screen at the airport was Benq. Benq and similar brands are on the border between cheap and good with a range of models from not quite tough enough for public use through to good solid commercial use. Ask potential suppliers about the fine print on public and commercial use.
A spill proof keyboard could deflect the main problem of spilt coffee and crumbs.
So how does Ubuntu survive?
First you install only the bare minimum Ubuntu then the Web browser. you set Ubuntu to automatically log in to the guest account and automatically activate the Web browser. There is little to write to disk and it goes into a RAM disk. You do not offer USB access or a DVD drive. You stop the worst Web site attacks by not installing Java and set the Web browser to not install anything else. You switch off the option to change options.
After creating and testing the first machine, you clone the configuration across the other machines. The work on the second and subsequent machines is trivial.
Prior to Ubuntu 9.04 there were problems with configuration options and browser versions. 9.04 requires a manual install to get a current Firefox. Ubuntu 9.10 has a current Firefox and misses in some other areas important in desktop workstations but nothing needed in a public Internet browsing machine.
The hardware can use the smallest slowest mainstream processor from AMD or Intel. AMD has some special low power chips of real interest.
You can also buy low power devices using technology designed for notebook computers but these options are currently more expensive and, at the cheaper end of the range, are too slow. The one use for really low power devices is to avoid using fans because of the noise and space wasted on airflow. Some display screens now have computers built into the log board on the back of the LCD.
20 years after the first LCD screen with a build in computer, many manufacturers are supplying LCD screens with built in computers and calling them nettops. You can buy a Benq 19" nettop for $500 and a 21.5" nettop for $750. The cheapest Apple 21.5" nettop is $1599. A nice looking MSI 21.5" nettop is $599. The $500 nettops look good for your Internet cafe except you will have to disable the DVD and USB.
Finding something without Windows inflating the price is the hardest part.