The factors determining the prices of financial options could be the following:

• The difference between exercise price and current share price: the more the option is in the money, the higher the price, the more the option is out of the money, the lower the price, namely, if the exercise price is higher than the current share price the value of the option is very little – the option is out of the money. Viceversa, if the current price is much higher than the exercise price of the option, the value of the option is in the money and it increases.
• The volatility: if the share price is very volatile, probably the option will be more expensive to buy or sell.
• Time to expiry: the longer the option life is, the higher its price due to the time value for money.

When in an equity market the call option is much in the money,we say that the put option is out of the money, as the current price is much higher than the exercise price. For this reason, it is fair if the call option is more expensive than the put option. On the other hand, when in an equity market the opposite happens, the put option is much in the money whereas the call option is out of the money. Consequently, the put option will be more expensive than the call option.