He can't help but make a little noise of acknowledgement and nod as Alucard mentions his black market contacts were gone. Strange didn't have any himself, but he did know a few people who were willing to not pay as much attention during his madness phase. That kind of counts and those were also gone.

As for the compliment, Strange shrugs. As he speaks, he gets back to work, walking past Alucard to stop at a different set of runes on a different rib. "Thank me if you want or leave the matter be if you don't. As far as I can tell, it's objective fact. Your personality leaves much to be desired, but you're knowledgeable about this sort of thing and know how to ask the right questions. I appreciate it."

And, most importantly, Alucard can give as well as he can take. Strange won't admit that he's kind of lonely and misses the sort of hashing out a theory disguised as arguing that he had back with his mentor when he was at university...but he super misses the arguing/talking shop that he had with his former mentor. This isn't exactly like it, but it scratches that itch.