As late as last year, companies that wanted to sell or market on a mobile device had to create a separate application, which meant high cost and custom software support. That's expensive.
A better path is HTML5
HTML5 is a new standard for web development that works well for marketing and sales. Require your development group to work against this standard and you'll have website, tablet and mobile application built all in one. It does cost more than just building a regular website, but it's far cheaper than building a separate application for each device.
Apps are Expensive
Back during the peak of "app" development, TechCrunch (http://techcrunch.com/2010/05/16/iphone-app-sales-exposed) surveyed over 100 mobile application developers on their application costs. The average cost for development was just under $7,000, and that's for a reasonably low level of functionality.
Increase the number of things you want the app to do and costs go up. OSXDaily (http://osxdaily.com/2010/09/07/iphone-development-costs/) reported average prices ranging from $12,000 to $50,000, with high-end and highly branded applications costing $150,000.
Add the cost to support the IPad, Droid, and other handheld markets, and you can see costs could become a problem.
HTML5 Lowers Costs
Solutions for HTML5 are more widely available. This means that if you say you want an HTML5 image gallery for your eCommerce store, chances are it's already been developed and your developer doesn't have to create it from scratch. People who build apps tend to keep their code secret, so developers can't leverage and you can't get cheaper development for common features.
Another benefit for HTML5 is that you don't need custom hardware. Your developer can simply adjust their browser size and continue testing.
So how much should you expect to pay for HTML5 development? It will probably be in the ballpark for a single app, simply because code is code and a feature takes time to develop, no matter the platform. However, remember that by requiring development in HTML5, that one app will support multiple hardware and that's a source of savings.
For all HTML5's promise, it's still a work in progress. It can't do everything. It was, after all, only introduced 15 months ago.
The biggest issue goes back to older browsers. Internet Explorer still holds 28% of the web market and HTML5 is only supported from version 9. For HTML5 to support older browser are a series of "wedges" that provide fallback support to switch features back to their older versions.
However, that's not too big of deal for mobile development as most mobile browsers are fairly new and support the newer standard.
HTML5 development also has to be more device sensitive as not all devices or browsers can support all features. The biggest issue is animation and video. If you really want older browsers to support the same animation, you may need to have it developed twice, once in Flash and once in HTML5. And that's a cost.
To Sum It Up
Simply put, use HTML5. You application will be future proofed and development costs will be far lower. You'll be clad you did.