I’m a keep it raw type of guy (if we weren’t on a comic forum that would totally be taken out of context). Anyways, like jcLu said, it’s almost a case by case basis for new modern books. 9.8 and if the book is hot, it might be worth the extra cost and effort to get slabbed if you want to do a quick flip.
I went over this in a post last year I think and concluded that unless the book gets you $150 or more after spending around $50 to $60 total to obtain the book, get it slabbed and shipping costs, it’s just not worth it, particularly if the raw books are fetching $100 or so.
Take for instance Naomi #1. I sold a raw book I bought for $10 for $110. After eBay fees and such, I pocketed around $90 or so. I think at the time, 9.8 CGC were going on average of $200. So yeah, there’s a bit more profit in there if you were able to buy it at cover, pay the slabbing fees and then shipping costs. If there’s any delays the window for top dollar could be missed and there’s also the chance the book comes back at 9.6 or lower.
The books I sold could have been 9.8 but they were likely 9.6 or so.
So use your best judgement and watch the trends. If a raw book in claimed 9.8 is selling for $100 while the 9.8’s are selling for $400 or more, that’s a no brainer if you know you got a 9.8 candidate.
As for slabbing in general, some do it just to throw into personal collection knowing the book has the extra protection. I myself, I just get top notch Mylar with Archival grade backer boards and I’m probably just as protected. Keep’em high, dry and don’t smoke around them.