Catalonia is 1% of the EU GDP
Spain doesn’t rely only on Catalonia and its debt is pretty low compared to other EU countries (keep in mind that 1300 companies and all Catalonian listed companies have moved out of Catalonia), bringing from now on income to other Spanish provinces. This includes the company of the cousin of the Catalan president...
The debt of the local government of Catalonia is actually the highest in Spain, Catalonia will have to take this with them if they want independence...
Madrid has actually taken over Catalonia recently, Navarra is also heavily productive as is Valencia.