With respect to an option, this cost is known as the premium. It is the price of the option contract. In our home example, the deposit might be $20,000 that the buyer pays the developer. Let’s say two years have passed, and now the developments are built and zoning has been approved. The home buyer exercises the option and buys the home for $400,000 because that is the contract purchased.
In search of a promising commodity option trade, it is important to look at whether or not the options are priced fairly. Option prices fluctuate according to supply and demand in the underlying commodity market. At times, options on futures prices become inflated or undervalued relative to theoretical models such as Black and Scholes. For example, during the "crash" of 2008 the value of put options exploded as traders scrambled to buy insurance for their stock portfolios or simply wanted to wager that the equity market would go down forever. The increase in option premium was partly due to inflated volatility but increased demand for the instruments had a lot to do with it. Those that chose to purchase put options at inopportune times and at overvalued prices, likely didn't fair very well.
The potential home buyer would benefit from the option of buying or not. Imagine they can buy a call option from the developer to buy the home at say $400,000 at any point in the next three years. Well, they can—you know it as a non-refundable deposit. Naturally, the developer wouldn’t grant such an option for free. The potential home buyer needs to contribute a down-payment to lock in that right.