7.8 million people have applied for CERB so far, not 200,000. An estimated 30% of Canada's workforce has either lost their job or had their hours/pay significantly reduced due to the pandemic so far, and the program is in place to make sure we don't have a huge amount of evictions, foreclosures, bankruptcies, etc. so that we're positioned well for a recovery.
Yes there is an estimated amount of fraud, and the government and the CRA have said that they will be auditing and reviewing anyone who collected money to ensure they were actually eligible, anyone who wasn't will be gone after for the money back or prosecuted criminally.
To answer "who is paying for it", in the short term taxpayers that are still working are helping to support people who can't, in the long term everyone will have to pay this down over time.
Edit: 7.8 million, not 3.5 million who have received it.