My question is, would there be a financial advantage if I merged all of these sites in to one domain, so that a single domain has 30 million pageviews?
That won't happen.
The metrics for each are separate. Perhaps a few can be combined and continue, but when you change anything (such as a destination) all kinds of heck will ensue.
You can't actually believe all the existing will culminate into one?
Traffic will be lost left and right, yet, IN THE END, you just might ended up with a REALLY GOOD USABLE site.
IF the 55 sites have anything remotely in common.
What you will REALLY ACHIEVE is fewer headaches, playing games, consolidating your efforts and kicking all those expenses (host costs, you will continue to pay registrations for the domains forever!), and having to put on 55 different hats each time you service a site with content.
What is readily apparent is a dilution of csdude55 ... 55 times. "All About Eve" has nothing on you! :) (joke, look it up ... it's a film)
Spread too thin, particularly if you are a less than 5 shop.
But the real question remains that IF you can actually consolidate all into one, did you spend the last x years playing split personality (sites) for nothing?
Or as lucy24 suggest, keep paying to host/dns fees as long as there's an income and don't rock the boat.
Every major change we've heard about/discussed at WW has never EXCEEDED the original that was in place before that change. There is no G love in that kind of change. Just keep that in mind.
There is one other consideration ...
Those of the 55 that under perform ... kick them to the curb, recover your time and effort (keep the domain name, never give it up) and change 55-1 ... or 35!
One thing that will benefit the web is sites that don't do well shutting down. (No ugly intended!)
1,000,000,000,000,000,000,000,000,000,000,000,000 -1 won't make a difference, but it is a start.
This really boils down to REFINE your product. Your Time. Your Effort. Your Assets/Cost. And if you have to ask, pretty sure you already know the answer, just need a kick in the pants to get started. Been there, done that, have the t-shirt ... and the memory of that wake up call. Grateful it continues to haunt me whenever I outgrow britches again.
OP ... the financial advantage is to manage your costs, your resources, and your biz. Do that and you will have won. You won't keep 30m traffic, but the traffic you DO keep will be better, and to the point. REGROUP and RESTART.