One company has become Wall Street's money tree

Pharmaceutical giant Teva agreed to buy Allergan's generic drug arm for about $40.5 billion on Monday.

That should cement the Israel-based company's position as the top generic drugmaker in the world.

It will also be great for Wall Street banks, which will reap millions in advisory and other fees.

Allergan has already paid out hundreds of millions of dollars in fees over the past few years, as it participated in a round of frenetic dealmaking.

That culminated in Irish-based Actavis buying Allergan for $66 billion last year and keeping the name.

Together, those two firms have generated some $780 million in investment banking fees for mergers and acquisition advice and equity, debt and loan deals since 2012, according to consultant Freeman & Co.

Now, the Teva deal should boost total Allergan-Actavis fees to about $820 million, according to Freeman.

Allergan adviser JPMorgan is in line to receive between $35 million and $45 million in fees for the deal.

Barclays and Greenhill, which are advising Teva, should earn somewhere between $30 million to $40 million, Freeman estimated.

And that doesn't include all the potential fees to come depending on the size and structure of the equity and debt package.