A typical Shopify Google Merchant Center Account Setup with NO optimizations will take between 2-4 hours of work based on complexity, number of product issues once live, etc, etc.
Individual product optimizations typically take between 15-30 minutes per SKU based on how much individual research needs to be done, and how often we can bulk edit certain attributes such as Product Type. It all depends, but the products come out individually optimized and that's a win!
Pay someone for a few hours of their time, and save dozens of your own hours!