The ...450 is the current part. With a quick google search the cheapest place I found it is around $550.
This link is one example. Interestingly, the prior version was only around $270, but given the potential for cracking I think I'd go with the newer version.
This link will tell you more than you probably want to know about EGR coolers. Interesting that (if I understand it all correctly) some of the revisions have to do with internal components, aiming to reducing condensates and subsequent corrosion. Perhaps this will also reduce carbon build up in the swirl valves/intake manifold, etc. Very interesting to me that some of the 35d's have at least moderate carbon build up (like mine - see
this link), while others have minimal to none. Could a newer EGR cooler minimize carbon build up as well?
Since I'm usually a glass half full kind of person, I'd keep telling myself that the upgraded part will not only be less prone to cracking, but is also less prone to developing carbon build up!
BTW - here is
another link about EGR cracking and attempts to get BMW warranty to pay for it.
Good luck.