I think it is worth the money, could be used as an awesome alternative to the bubble zombie routine by Losander. But if cost is something that is a factor, you could look for the abbot dvd "magic for kids" or something like that, which I believe tells you how to construct your own.
Here are the pros and cons of doing that. Pros: Cut back on cost, some degree of customization. Cons: You build it, you miss out on having a pro. built prop, you have to find the necessary supplies.