ffrr, perhaps you just aren't looking hard enough?
Whilst Frontier haven't
explicitly stated XB1 sales of ED, information
has been available.
Since the ED Kickstarter inception The now defunct
Kickstarter Backers' Page was updating more-than-hourly the
'Raised' and
'Backers' figures for Elite Dangerous.
Exellent post, very informative, and unlike some contributions to the thread, containing actual verified facts...
This information was only available to Kickstarter Bac
kers with a valid login.
However, a kindly soul (and Elite Greeter)
INaeem was regularly updating the thread
Current funding through kickstarter, backer’s app and zaonce store
BTW Thanks again INaeem for your
'Welcome Home Commander!' post when I left the Kickstarter Comments section and graduated to this Forum %^]
The Kickstarter Backers' page has since ceased reporting 'Raised' and 'Backers' figures -
but not before XB1 launch.
ED XB1 launch (GPP) was on
15th June 2015
Here are the figures before and after that date:
5th June - 17th June
5th June £17,146,473 raised - 551,875 backers
6th June £17,152,818 raised - 552,983 backers
7th June £17,160,101 raised - 554,434 backers
8th June £17,164,223 raised - 555,731 backers
9th June £17,167,611 raised - 556,579 backers
10th June £17,170,563 raised - 557,301 backers
11h June £17,173,558 raised - 557,816 backers
12th June £17,176,049 raised - 558,935 backers
13th June £17,179,303 raised - 560,419 backers
14th June £17,182,741 raised - 561,936 backers
15th June £17,185,310 raised - 563,025 backers
16th June £17,187,585 raised - 574,694 backers
17th June £17,192,622 raised - 611,367 backers
Pre-XB1 launch (from 5th to 15th) the daily average was ~1,000 backers(units)/day
Post-XB1 launch (from 15th to 17th) the daily average was ~24,000 backers(units)/day
Removing the Pre-XB1 daily average, that yields ~23,000 XB1 units/day immediately after launch.
That was 6 entire months ago - during which period the game has subsequently moved out of GPP and into full release on 6th October 2015.
So, a further 2.5 months on full release.
The XBox Store page for ED currently shows 7,874 reviews with an average score from these user reviews of 4/5 (...would interdict again 
Now, it's anyone's guess as to what proportion of XB1 players bother to review a game, but if we take the Steam Store as a starting point:
ED
607,379 'owners' and 10,330 reviews (1.7% bother to review)
EDH
34,248 'owners' and 397 reviews (1.16% bother to review)
So, let's pessimistically say that for some inexplicable reason 10 times as many XB1 owners bother to review ED on XB1 as for Steam (~10%)
Those 7,874 XB1 reviews would then represent at least 78,740 XB1 'owners' (...and potentially a lot more if the actual percentage bothering to review XB1 games is more like the Steam percentage - if the percentage bothering to review for XB1 is vastly different to Steam, can anyone explain why that might be?)