Yes, It is possible under various circustances.
If the blog is on a popular niche and traffic then the blogger can make most out of it.
If he set proper chanels of money from the blog traffic it will be possible to make $87,000 per month. He may be driving his traffic the right ways to convert them into sales, subsciptions etc.
If you want to clear more about it just ask him the way of monetization of the blog (adsense,affiliate marketing, social media etc).
In my opnion he must have set multiple monetize method on his blog.
Thanks
seoboyz