A number of software developers have begun adopting subscription payment models, from Adobe to Microsoft. And since the previous one-time payment models acclimated consumers to doling out hundreds of dollars in one chunk, many SaaS providers assumed an annual subscription rate would be preferable.But it turns out that many SaaS providers have had to adjust that idea and have begun offering monthly subscription plans, and Microsoft is the latest software developer to join the fold. The company announced that it has begun offering a $6.99/month subscription plan for Office 365 Personal and $9.99/month for Office 365 Home. (Office 365 Personal allows subscribers to run Office on one PC/Mac and one tablet; Office 365 Home allows users to run Office on five PCs/Macs and five tablets.) Annual subscriptions rates are usually $69.99 and $99.99, respectively.Previous research has shown that consumers can be fickle about how much they’re willing to pay for a product or service depending on the payment model, and software developers adopting SaaS subscription models have learned this the hard way. In December of 2012, a study found that 51% of survey respondents said they would be more likely to purchase a subscription to Adobe’s Creative Cloud if the company dropped its price from $50/month to $30/month, even though the $50/month subscription price still offers substantial savings over Adobe’s previous one-time payment when amortized over the normal length of software use.The same may be true for publishers looking to turn reference books into subscription-based digital assets. You may or may not make more on a subscription model based on consumer attitudes, not just the usual length or duration consumers tend to usse your products. So be sure to do plenty of market research and run a beta test or two, if you can.