In my opinion it is much more important that a museum spend more money in its collection than for an expensive building. Visitors pay for the objects, which are in the museum and not for viewing the building!
It is very important that a museum building is very stable and safe of flooding in order to protect well the objects in it.
Sometimes a museum was erected at a historical site in a building, which has a more or less content with the presented objects. Here two examples of Germany:
Historisch-Technisches Informationszentrum Peenemünde, situated in and around former Peenemünde Power Station
Sendermuseum Königs Wusterhausen, situated in former transmitter building of Königs Wusterhausen transmitter