What parts were they using? I got charged under $150 AU at a volvo dealer
using my parts. Shocks range from a few $$ to many $$$. If you want to know
how easy the job is then use google. There are many links showing the
process. I've done mine a few times this last year (Playing with spring
combinations) but you do have to be careful.

AJS

That's a pretty good price for parts and labor.  I would assume that just
the strut inserts are being replaced, not the whole strut which would
include the coiled spring.  Labor on front struts is a lot more than rear
schock.  A shadetree guy can do this, it takes a couple of special tools on
the fastening nut at the top of the strut.  You can see this nut under the
hood by lifting its black plastic/rubber cover.  You can get a special
offset ratchet wrench socket from Pep Boys or Autozone tool "loaner" program
to handle this nut.  Haynes and Bentley books for the Volvo 240 can walk you
through this.

After finishing the job, the front end needs a fresh alignment job.  Only a
very good shadetree guy can do this without the alignment equipment found in
modern garages.

I just did the same work you mention on my 91 240 last year on all 4
corners.  At the same time, I also replaced all ball joints and suspension
bushings, which often are the cause of clunk noise.  On my car, the ball
joint boots and the bushing rubber was cracking, indicating time for
replacement.  I did not replace the top strut mount bearings.  I used Boge
turbo gas shocks and struts, which are touted as very similar to Volvo's.
The rear shocks made a slight rapid tapping noise even when new, so I
switched to Volvo brand (which I'm told are the Boge entry-level shocks).  I
would have saved myself some money and labor by going with all Volvo parts
to begin with.  When completed, this job will provide an almost brand new
feeling ride again, and shouldn't need any more attention for another 10
years.

http://catalog.buyautoparts.com/meridian/ib/wizard.jsp?partner=meridian&clientid
=buyautoparts&baseurl=http://www.buyautoparts.com/&cookieid=1BR0SIZDM&year=1992&
make=VO&model=240--004&category=L&part=Strut+Insert

parts=150
labor@1.5 hr/side@$80=3x80=240
alignment=75
I guess 450 does not sound too high!

diy:
http://www1.autozone.com/servlet/UiBroker/?UseCase=C001&UserAction=answerRequire
dQuestion&Parameters=%7C%7EWITH+NON-REBUILDABLE+O.E.+STRUTS&PageSync=5