Transformer Outputs Voltage High Above Expected Voltage
It's a bit of a misnomer to call the flyback converter magnetics "a transformer" because it is being used as an inductor with a load so the inductance is chosen to support the low DCR conduction losses and same for the secondary.  

Normally the inductance ratio is adjusted to give around 50% duty cycle for the desired load or less at minimum losses. 

Basic math

The energy storage density has a limit to transfer about 100~200W max before the topology becomes less efficient than a forward converting transformer topology where the transformer no longer has to store the energy being transferred as it is coupled by the mutual coupling with a much lower impedance path.