I noticed this thread and thought I would put in my two bits worth ( as someone who developed a iPhone app).
Quite frankly the prices quoted for the actual app and monthly hosting are not unreasonable if you compare them to starting from scratch and going it alone.
However, what is not addressed is the fact that the mobile phone app market is fundamentally different in many ways than having an online presence.
1) Build a web site and visitors using Explorer, Firefox, Chrome, Safari, etc. will all be able to visit it. Yes, there may be a few minor quirks on less known browsers but generally if the site is built well they will all work.
Smartpones, yikes multiple platforms, multiple coding. Blackberries, require a Blackberry app, iPhones and iphone app.
2) With a little SEO work your website will pop up somewhere on the first few pages of search results on Google, Bing , or Yahoo. With a bit more work you might even get fairly decent placement for key search terms depending on your market. Some of this work involves time and sweat, but little money. For the price of a Smartphone app you could find an SEO guy ( maybe even Ryan) to help improve your websites rank.
There is no web equivalent "search engine" for smartphones to allow you to "window shop", You want an app you look for that app for your phone platform and load the app, don't like it or the products offered....too bad. Look again, load another app, start over.
3) The individual who buys flowers once or twice a year simply visits your website by choice or by accident when they need flowers, no commitment of any kind prior to or after the purchase. If they like what they see they can buy with little hassle.
Smartphone apps are not quite so carefree, first a consumer needs to find an app that interests them, then possibly pay for it, then download it. A lot of time and effort for a one time spur of the moment or occasional purchase. For the frequent flower buyer its a lot easier to shop on a 21" monitor than on a iPhone screen, plus your not stuck looking at it everytime you use your phone..
4) A smartphone app needs to be marketed in exactly the same way as you market all of the products and services you sell. Frankly it is a lot harder convincing consumers to load an app than to visit a website, plus you are dealing with a much smaller group of users (a particular smartphone platform versus the entire internet) and among those an even smaller number of potential flower buyers than you are have on the web.
My advice (IMHO) is that the average florist simply does not have the resources to effectively market a smartphone app to justify the investment. They can probably achieve a higher return by focusing on SEO for their website and on their B&M business.
Just my thoughts for what they are worth