[ig1]

It's not just the cost of reviews though. Most new journals take decades to become break-even, they're typically subsidized by cashcow journals (big names with good reputations which bring in solid revenue).

Launching a new journal is a non-trivial process, you have to convince people to publish in it, you have to convince peer reviewers that it's worth their effort, etc. You have to have a marketing and sales teams that gets it into the hands and minds of researchers/libraries/etc. Then follows several decades of brand building before you make any real money. Many journals don't make it and die and publishers have to swallow the losses.

In practice OA has other solutions (author pays) to fund this, but it's far from a free lunch.