The Cut Scene reckon that, according to "a good source", the add-on has sold "around one million units on Xbox Live". Microsoft can't confirm this number, but it does sound awfully familiar.
If that unconfirmed number checks out, that equates to around $20,000,000 in revenue for Microsoft. Which, yes, for something like Xbox Live probably is a revenue record. But is it a sales success? There are 6-7 million copies of Grand Theft Auto IV out there on 360, so "only" a million sales of Lost & Damned sounds like a (relatively) disappointing return.
Why it's increasingly important that there's no DLC in NPD [The Cut Scene]