As for longest to make, yes you could use 3rd party stuff to cut down on the time, though it could restrict you on what you can do so getting something that works for what you want is important. Even mixing a client up with asp/php parts is possible (starpeace uses asp for parts of the game).
As for the money part, it's all about percieved value, a downloaded client based game has more percieved value than a browser based game. So it's easier charge people more, however it is harder to gain those users, so while you make more money per person, you will also have less people. whether you make more money overall one way or the other is hard to judge and depends on the quality of the game and the quality of your promotion.
tolik: yes, html/php/asp will use a lot more bandwidth, i know this very well as my mmo uses both, on average a user has about 700B/sec usage and the web parts are about 56k on average on the page plus images. The images do get cached by the user but the users can access page's every 10-20 seconds and the web parts arn't the most important part of the game. It's the extra html tags and rubbish that up's the web parts as the actual useful data is a very small part of that. Stripping the html stuff and about 1-2k per page is useful.
As for the app data, check out both the developer and application leaderboards user DAU (daily average users) and see how quickly number 1 zagna at 64.8million go's to number 40 aa at 0.5 million. It's a steep drop in only 40 developers from a list of 33230 developers. Thats not even taking into consideration the number of those which are silly wee apps that get high numbers of a month or so and then die.