The insurance premium depends on your age, but it seems absurdly high.
To get a better handle on the payments, I'll split it up into two parts:
You pay 30,000 per year for 15 years (450,000 total), and after 15 years you get 500,000 if you live; if you die, they keep what you paid and you stop paying. Not a good deal. 11% interest after 15 years and you lose it if you die.
You also pay 20,000 per year for 15 years (300,000 total), and if you die, your heirs get 500,000 and you stop paying. In the UK, as a 30 year old smoker you pay about £6.80 a year for £100,000 life insurance (risk only), that would be £408 per year for £500,000. You are paying 20,000 per year.
Xyroid, you asked what's the benefit of the policy: The benefit is filling the pockets of whoever sold it to you.
Edit: Looking at their prospect, the "500,000" is a meaningless number. They suggest that your payout after 15 years should be substantially higher than 500,000. Much of it is not guaranteed, but estimated, so you will get more or less money, depending on probably how well they invest your money. So this is not the ripoff that it first seemed to be.
Premiums for insuring a payment on your death should be really low unless your age is 50 years or upward, so you can mostly ignore this. Which means this is not really a life insurance at all; it is a tiny bit of life insurance, together with a huge 15 year savings contract.
You should find someone who is willing to go through the numbers with you and figuring out what you signed up for. But I must say, you should have asked your question here before signing.