Just looked round the web and the best price I can find on a 50t compact Ultegra ring is around £70.
Nothing in stock at CRC and they're asking £87 when they arrive on 16/11.
The German cheap sites don't have any.
What's going on in the world?
Could be worse, the holow ones on DA are £140!
Plenty of cheeper and lighter options, so I guess you're paying £40 for the forged shape and polished finish as opposed to the cheeper brands CNCing them from sheets of 4mm aluminium and a plain anodized finish.
For what crank? Ones for 6650, Rose has them for £55 ish, for 6750 Rose has black in stock @ £58 ish, one week lead for grey @ £55
http://www.spacycles.co.uk/products.php?plid=m2b0s149p296
and
http://www.spacycles.co.uk/products.php?plid=m2b0s149p436
I use a 54T and had no issues at all with in. Although having said that if you are using teh newer style Ultegra chainset it might look a little odd.
You could always buy this for £80 and sell your old one?
http://www.chainreactioncycles.com/Models.aspx?ModelID=11787
I've got a SH 6600 compact in the shed with good rings you can have for £50 posted IIRC.
Tim
Currently using the 6600SL ice grey from 2008. Can I use those 6650 or 6670 rings on my 6600?
What's the performance difference between different makes of chainring?
Assuming that is one of these:
[img] 
[/img]
Which is what I have only chrome/silver.
The original Shimano chainring looked a little smarter, and did have shifting ramps which helped when moving upto big ring. However in reality it hasn't made much difference, got to admit I hardly ever use the small ring either, and for £12 you can't go wrong!