The premium is everything ! For valuing index & stock options the strike, spot, interest rate and dividend yield are all constants (99.9% of the time ) the only variable is the Volatility which makes up the premium. I traded FX options for an institution, we would only trade the volatility, the other factors being consant, the volatility being the premium.
Just reading his post again I think he wants to know ,if he is obliged to take delivery of $100 worth of shares at some point then surely his margin can not exceed $100 at any stage
In your example from earlier, where the put was SOLD at a $100 strike and the stock rises sharply to $5000, the put is worthless. My max margin is $10,000 (100 shares *$100) per contract, period. At a price of above $100, the margin is a percentage of the total exposure - depending on the broker, below $100, the value ITM plus a percentage of the remaining exposure. Who (as an owner of a $100 bought put) would put stock to me and get $100 when he can sell it on the open market for $5000? IV or HV have absolutely nothing to do with margin. Margin is based on relatively simple mathematical formulas that calculate the broker's exposure of exercise and delivery. The greeks go down the toilet at exercise and for those who are holding to expiry. On the Call side, there are different issues. For Puts, I still say you are wrong.
WTF !, it may seem bizarre to you but IV does have an inlfluence on the price! which in turn has an effect on your margin calls! and to think I missed my "out " reading that !