Last year I had a huge amount of miles on Lufthansa M&M. Redeemed, they would have been worth about €70 against a ticket.
By using them at the LH online shop, I got €300 of Radisson vouchers and a couple of Tommy Hilfiger shirts (admittedly not something I would every normally buy) worth about €200, total €500 as against €70!
I have about 70000 Avios points. Redeemed against a ticket to South Africa they are worth about £100, less I think, but if I use them for short European journeys, I can save up to £100 per ticket for 4500 points, making them worth potentially £1500.
These schemes are all a bit of a con but the system can be beaten.