I guess I don't know what would be hidden - it's all pretty clear on their website and initial estimate they send you. It's the package price, plus a per head fee. Then if you want to add cake, more flowers, the photographer, etc. - then it's more. But the exact cost of those is listed on their website - it's the only place I've seen where it's so spelled out actually!
And I agree with Rachel, not sure I'd call that a "lower priced" option either. Or at least I don't know how you can compare that WC with Caletas. With her, you'd be paying for her services, whereas with Caletas you're paying for the services of Nicole and Kelley, along with the site, the food, the transportation, etc.