The van looks luxurious, so maybe that's worth something. The rest looks much like my US$30 cruise, except much more hurried.

I did no advance research--just rode my 250 into town, found a friendly little hotel up a side street, and booked a full-day cruise through their desk. My $30 included a substantial commission for them, so there's certainly some slack in the pricing. We spent hours at a time walking thru caves, kayaking, hiking to hilltop views, ignoring pearl salespeople, and (in my case) napping between sights. The heavily-hyped attractions (some of which are listed in the linked description) were actually less appealing than expected due to the thick clots of boats or crowds of perambulating tourists at each one.

I've no intention of debating the relative merits--just pointing out that you might do better to base in Halong rather than Hanoi if you have time. There are bays to the north as well as more remote areas which are reportedly far less crowded and at least equally scenic.

I didn't find Hoi An particularly appealing, but then again I wasn't there for beaches or custom tailoring. The usual response has been "Yes but the surrounding area is very pretty," which is true, but applies almost everywhere throughout Vietnam. Tastes, like mileage, vary.

Hope that's helpful.

Mark