Just bought 105,000 miles for EUR 1,650. Exactly for the kind of situation described by other posters earlier on: topping up the balance to have enough miles for a specific award. Excellent deal for my needs in this particular situation:

I wanted to transport six family members one-way from Paris to Vancouver to join a cruise, in J class:

• Cash price for the one-way ticket is EUR 5,758 per ticket
• Award is 92,500 miles per ticket - so this is a good use of miles in my mind
• I was short about 100,000 miles to get award tickets for everybody (had enough for 4 people, plus 84,000 miles left after that). So I had a choice:
  • Pay those two tickets that I couldn't get on miles in cash: EUR 11,516 (but have about 84,000 miles left over for something else in the future)
  • Buy missing miles for one ticket (about 8,000 miles) and pay the last ticket in cash: EUR 165 for 8,400 miles + EUR 5,758 for one ticket = EUR 5,923
  • Collect the missing miles to get all tickets as award tickets: as Plat I get 8 miles per EUR spent. For 105,000 missing miles that would have been EUR 13,125. Indeed, it would come with some actual flights, but I don't see a point in flying somewhere only because it comes with the thing that I actually need, i.e. the miles. I might have earned those miles at some point anyway through normal spending, but by then the award might have become more expensive. And I can still use those miles for future trips once I have earned them
  • Buy all the missing miles to get all tickets as award tickets: EUR 1,650 for 105,000 miles

Buying the miles for the sake of miles (special mentioning for some posters: *I bought miles to get miles so that I could top up my account to afford a specific award*, not caring whether a flight is an additional product that comes with it) costs me less money than all the other options:

• EUR 9,866 less than buying both tickets with money
• EUR 4,273 less than buying a few miles to top up my balance and get one ticket on miles and another one with cash
• EUR 11,475 than collecting the miles through flying

Those are very substantial amounts of money, at least for me, and I am glad I had the possibility to purchase miles and keep that cash instead.