I am aware that it is possible to get a visa on arrival but I was wondering if anybody could find a source that says how much it costs.
City of Departure: SFO
According to the Qatar e-government website:
Residents of the 33 approved countries can obtain a Tourist Visa upon arrival. The visa can be purchased for a nominal fee at the airport or port. It can also be issued online instantly prior to travel. This visa is valid for one month and cannot be extended.
The visa costs are:
Visa issuance fees: QR 100 for each visa, QR 50 for each accompanying person and QR 200 for overstay fine per day.
At the current exchange rate this works out to ~28
This visa is valid for one month and non-extendable.