On a rescue dog like this, likely minimal. Maybe the thieves thought it was a purebreed?

But on a designer or purebreed dog? Pretty large. People will buy puppies / young dogs off craiglists (Example One: https://boston.craigslist.org/sob/for/d/norton-french-bulldog/7598631116.html Example Two: https://boston.craigslist.org/nwb/pet/d/boston-female-mini-poodle-mix-puppy/7601380906.html) and ask minimal questions about where they came from. For someone looking to make a quick $500 - $3,000 it's very easy to grab a dog off the street and then resell it.