Pricing and services:
Note: As of April 2012, Cosmo is actively kicking third party photographers off the property if security sees you; I can't advise using them for any services at this point because their in-house photography is mediocre and overpriced, so you're going to get screwed either way.
From a strictly chapel standpoint, the Cosmo's offerings are pretty weak and catered mostly towards people who are drunk and decide to get married. They have three packages ranging from $80 to $195 (add $90 if you want it to actually be a legal ceremony). The top package includes the ceremony, a bottle of cheap champagne, two gimmick rings, two photos, party favors, two t-shirts, a gift bag, some cake and guest list spots at their clubs.
Oh, forgot to mention, the ceremony is performed at street level in front of everyone walking by on the strip.
Here's an article that better explains, with pics at the bottom:
Now, what people really tend to use the Cosmo for are in-suite weddings and receptions due to their great location, trendy decor and incredible views thanks to what typically include wrap-around external balconies since the largest suites have those. See the Cosmo article in the resort section for more info on that. They do have official packages that are based around in-suite offerings; it takes communicating with them though as they don't have the info on their site and I haven't been able to find a definitive price sheet to put something together here. Will update as more info becomes available; they just came under new general management to start 2012.
People who have used this vendor (sorted by date) and link to the review:
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