Here are the 13 most expensive stocks to bet against

• Betting against some company stocks can be more expensive than owning them.
• Clovis Oncology, currently the most expensive stock to short, boasts a 109% borrow fee according to data from S3 Partners, a financial analytics firm.
• Here are the top 13 stocks with the highest borrow fees, according S3 Partners.
• Read more on Business Insider.

Short selling, or the practice of betting that a stock's price will fall instead of rise, can be an expensive business.

That's because the price to borrow shares of some stocks can be more expensive than owning them, data show. For example, traders are currently paying a 109% borrow fee to short shares of Clovis Oncology, according to data from financial analytics firm S3 Partners.

That fee has put Clovis Oncology at the top of the most expensive short list. The company surged into the top spot after its fee jumped 69% in the last two weeks, Ihor Dusaniwsky, the managing director of predictive analytics at S3, wrote in a Tuesday note.

It's likely that the stock's borrow fee could climb even higher, Dusaniwsky said. "New stock borrows are going at over 400% fee today as there are very few shares left to borrow. CLVS stock loan recalls are also hitting the street in size," he wrote.

Borrow fees can be detrimental to traders betting against costly stocks. "High stock borrow costs can eat into expected Alpha making an attractive trade fall below investment thresholds," Dusaniwsky wrote. "Or an unexpected increase in borrow rates can turn a home-run trade into a run of the mill single."

Fees can be hundreds of thousands or even millions of dollars each day. Currently, traders are paying more than $1 million per day in short financing costs on the stock, according to S3.

While right now, it's the only stock that costs more than $1 million per day to bet against, that could change soon, said Dusaniwsky.

Two other companies on the list, Nio and Canopy Growth, are seeing borrowing costs rise. "There will probably be a triumvirate of $1 million borrows in the very near future," Dusaniwsky wrote. In addition to Canopy Growth, four other cannabis companies are on the most expensive shorts list - Tilray, Hexo, Aurora Cannabis, and Aphria.

Here are the top 13 stocks with the most expensive borrow fees, ranked from least to most expensive according to S3 data.