If you are a long term investor and hold warrants, you buy now the number of shares your warrants would be. That way, if the price goes above the warrant exercise price, you can sell the shares you buy now, exercise your warrants at the lower price and pocket the difference.

If the price does not go above, then your warrants expire, but you still have the same number of shares, only at a lower price than the warrant price. So, you've saved yourself some money and still have the same number of shares you would have had should you have execised the warrants. Again, this is only if you're a long term investor.