going this route ... why do the major software manufacturers offer student versions ? ... (I'm thinking of adobe products specifically)
Get people hooked on using it... so they'll buy it for their commercial projects.
If you are going to make money from your site then you can afford to pay for it.
If not ... why not use their free version ? They are a business after all and out to make money. They are providing support ... and a lot of features ... timely bug fixes if any are required ... so I've no problem with their pricing model and their restrictions on use.
As you said there are a hell of a lot of CMS flavours out there .. they aren't forcing you to buy it ... (I've never bought EE) .. the price has put me off it. especially for smaller projects. Telling a small customer year thats going to be 250 dollars before I touch your site .. and hosting and domain name costs ... would freak a lot of smaller clients.
(of course this probably just means I'm dealing with the wrong type of clients)