> How much extra time has to be spent on putting in place a process for data deletion?

Account for deletion when designing the product. When considered from the beginning, the cost is typically negligible. It's only when shoehorned on the end that it gets expensive.

But... companies have had two years of notice about this. Any projects that have been running for fewer than two years have had plenty of notice. And it's not only the government who requires data deletion - it's your data sources (like Twitter) and your big customers who write it into their contracts.

Just plan for being able to delete data. You are gonna need it.