OK, so I know that if I want 100% status miles, I need to have at least a 'Flex' Class fare. Obviously, I'd like to save as much money as possible when flying internationally to South-East Asia, so I'd like to know how the various Flex fares compare for cost.

For example, I know that a Q fare is less expensive than an M fare (which is counter-intuitive), but I'd like to know how all relate and if there are any restrictions on eUpgrades with any of these fares.