If 'money chasing' was an adjective, then the sentence would need to be.. "There ARE now so MANY money chasing companies that.." But, looking at the sentence as it is written, the use of 'there is' is correct.. There is now so much money (uncountable noun) chasing (verb) companies (direct object). I think the sentence is basically saying people are so keen to invest in companies now, that a company's valuation can be inflated or incorrect (due to it's popularity).

Here the word money is singular (uncountable) eg. There is now so much money being distributed. There are now so many companies closing down. Hope this helps!