Moving to the web is any business-man's wet dream moving closer to perfect
price discrimination. Adobe CS3 with its several different reincarnations are just some of the first baby-steps towards charging each person what they can afford to for the software.
In the olden days everybody paid the same for a widget. Then an Englishman Arthur Cecil Pigou realized that different people value each good differently - CS3 is worth maybe $50 for a college student, but a pro could and would pay, say, $10000 for the same software. Early attempts at price discrimination in the software world included selling "pro" versions with all the bells and whistles at a "premium", and the "lite" version with the rudimentary features.
The reality is the other way around: the bells and whistles have already been developed, so including them in software doesn't have any additional cost in software world. But since not all people can afford the full version of PS, they came up with Photoshop Elements which sells at a discount compared to the full version. Adobe
could sell PS at Elements' price and still make a killing, but price discrimination allows them to extract more money from their customers. Beautiful. At least for Adobe.
(It should be noted that price discrimination isn't some nefarious plot despite the unfortunate term. Nobody is paying any more than they want to pay for it - that would be extortion or coercion. Price discrimination does allow companies to extract more marginal revenue from their customers, which in turn leads to increased revenues, and increased shareholder return. And perhaps even more and better features in the future. It also means that those people who would normally not be able to afford the full product can enjoy many of the benefits of the product without breaking the piggy.)
If (when) PS moves to the web, Adobe can not only charge per usage, but they can also charge per feature or plug-in. Then those who use only the curves and healing brush would pay, say, 50 cents per hour of usage, but those who want multiple layers, CMYK color and HDR would pay $2.50. The possibilities are endless, and it's only the market (us) who get to delineate how far Adobe et al can go with such tactics. Amazon tried price discrimination, but pulled out soon after people recoiled. It is much easier to justify price discrimination with software due to differing versions, though.
Price discrimination is a very interesting economic topic, but I won't bore you any more.