I believe MS should try and remedy the problem by allowing third party app stores / download sites, that get a cut of software sales. Therefore if a user downloads an app from a third party app store / download site that leads to a sale, the third party could get 10% of the sale, while MS gets 20%. This would provide a financial incentive for third parties to compete and get the most sales of software, at the best prices possible. Just require third parties keep free software on their sites to a minimum - of say 10% or less. Popular sites such as amazon.com, download.cnet.com, downloads.zdnet.com, and softpedia.com, could be invited to participate.
When developers upload their apps, I believe they should be allowed to elect to be listed by these third party sites, and they should be able to specify the prices of their apps, as well as in-app purchases, for each of these sites - the way a desktop app can list at different prices, from one online store to the next. They should be able to elect not to be listed in the Windows 8 app store, and users should be able to download their Windows 8 apps directly from these sites, without ever coming to the Windows 8 app store - since this would undermine the whole effort. (Please note in the above, MS would remain the exclusive hoster of Windows 8 apps.)
I believe the above would lead to better prices for Windows 8 apps, and a strong growth of quality apps. What MS would be doing, is allowing for Windows 8 apps to be listed under the same model that works for desktop apps. Remember, this is about keeping rich Windows 8 apps away from the Windows 8 app store, because the low prices in the store, are undermining the development of this category of apps.