Don’t under estimate the effort and risk they took. You can see enough in the three cruddy old pictures to guesstimate the amount of work they did.
Full kitchen remodel. Non-supporting wall removal. Wood flooring (looks like laminate). New bathrooms, new appliances, ceiling work, wall work, paint through-out.
Basically, a new home.
If the original purchase price was $450K and the new purchase price is at $675K, unless the buyer has the expertise, contacts and know-how, to do it all at once, I suspect they’d actually spend $200K to piecemeal the various remodels together with contractors and live in a construction zone for 2 years.