Moneys do not, so far as we can tell, have the capacity for a truly abstract currency system. They can exchange items in a barter system, and some forms or courtship exchanges may qualify as a primitive market form of prostitution. Despite this, monkeys cannot buy happiness.
There are a few facets of this statement which demand attention. The first, as stated above, clearly proves that monkeys, as consumers, cannot buy happiness with any significant form of token economy. The other aspect of the statement, and one less provable, is that monkeys as a currency, cannot buy happiness. Therein lay a much more complex set of problems.
It's simple to say that monkeys can't buy happiness because they physically cannot purchase the ice cream cone that would lead directly to their happiness. They also lack the understanding of why the vendor would exchange their paper currency for a larger volume of coins. This would confuse and anger the monkeys and probably would result in the flinging of feces. The more complex question is; can a consumer of happiness purchase said happiness with a given quantity of monkeys? The conclusive research says no, but the reasons are counterintuitive.
A consumer cannot buy happiness with monkeys as currency within the framework of any known exchange because of the simple fact that they are a self-generating source of happiness and so cannot be spent. Monkey antics and pranks are a source of laughter and fun so if they were a source of currency they would automatically generate interest. This is a difficult concept to grasp but monkeys may be a new source of wealth within the economy if we only use for that end. Monkeys as currency cannot buy happiness but are indeed a renewable resource of it.
The love of money is the root of all evil but that's just because we refuse to recognize the virtue of a monkey based currency exchange. The love of monkeys can be the root of charity, compassion, and altruism. Monkeys can't buy happiness, they are happiness. To prove it go to a zoo and watch them for awhile. The statement that Monkeys can't buy happiness is true in both interpretations addressed above but it is misleading to discount monkeys in any way. Monkeys led us into space and they may yet lead us to sustained economic progress.