Just my little story:
I obtained my JAR Multi-CPL-IR as I was in the Swissair program and was supposed to join the airline sometime last Fall. (We all know what happend to SR :-( but my comments are still valid). Because of no Swissair, I'll be with Swisswings from next month, flying a Dornier 328.
I was an integrated course and we spend about 35 hours on a PA-34 Seneca for the Multi-IR part. Skill test was divided into two parts: one flight for the IFR rating and one flight for CPL rating.
For the CPL part, I found the skill test to be almost just like the PPL, except for slightly tighter tolerances and that extra engine to handle. (Conditions were CAVOK but winds on ground in the 20 - 25 kts, with perhaps 8-12 kts of crosswind).
If you don't plan on flying twins, you may not need the extra costs. However, if an airline is the final goal, then you've got to handle a twin. But it's not that difficult; your "dead-engine" leg may get sore but that's all.
What is difficult is not to forget to fly at 65kts on final with a single engine a/c :-) !!!