When I googled cost of borrowing shares to short, got the following answer:
Cost of Borrowing a Stock
The cost of borrowing a stock to short can vary but typically ranges from 0.3% to 3% per year. The fees are applied daily. The borrowing fee can be much higher than 3%, and can even exceed 100% in extraordinary cases, as it is influenced by multiple factors. For example, similar to loan costs, the lender charges a leasing rate. This leasing rate for margin varies by the broker but is typically driven by whether or not a stock is "easy to borrow" or "hard to borrow."
If there's a great demand to borrow a stock, the borrowing rate for Shorting will often be higher than if there was little interest in borrowing the stock. The laws of demand and supply apply to the cost of short selling as well.
Say if 1 person would have shorted all the 150 million shares at a strike price of $1 and an interest rate of 3%, the daily fee would be 3% x 150 million / 365 = ~$12,400 per day. If total days of outstanding 20 days, the cost would have clocked up to .16 cents/share over the 20 days.
Doesn't seem to drastic at 3%, but we don't know the interest rate being charged.