The short answer is "buying in bulk". Typically, the longer someone stays in a property the cheaper it is per night. Another reason short term rentals command a higher price is because they are typically furnished properties (set up with furniture and ready to live in). A guest (tenant) can arrive with just the clothes on their back (or a suitcase full) and stay comfortably in the property.
You have choices when it comes to financial investments. Your main options are Stocks/Bonds/Funds, Currency/Commodities, Businesses, and Real Estate. Short Term Renting is an alternate and specific type of of real estate investing. Real Estate investing is primarily focused on either commercial (businesses) or residential (families) type properties. Short Term Renting typically focuses on residential properties by renting the property on a short term basis (i.e. daily, weekly, or monthly). There is higher risk to this because there is greater chance of vacancy (someone not staying in and paying for the use of the property) however there is greater potential for reward because when someone is staying in the property they will almost always pay more for it.
The amount of money that can be made with your short term rental varies on many factors. First your location will be one of the biggest reasons your vacation is successful or not. Also, how well you market your property so that people searching for short term rentals can find you when they need it is another big factor.