Hello The price of game engines range from 100 usd to 100.000 usd The point is that you can not see so many differences just going through the list of features Is it mainly a marketing issue ?

There are differences:
speed of course
support
and you cant deny that the new cry engine for example looks much better than some other 100$ engines..so...there must be a difference in features

Well the price range can differ even more (for example, the Unreal engine goes for like $750,000), though its hard to say if its really 75,000 times better than an engine that sells for $100. I have tested numerous engines and the features are not the same at all. I agree that when you look at a bullet-point list of features, they all look similar, but thats where the similarities end. When you actually work with an engine, or at least compare demos, there are many differences.

First off, many engines tend to pad the feature list with half-implemented or undocumented features. Others may support the features you need but require strange work-arounds to get them to work like you want. Other engines simply don't support the features. Before you shell out any money, make sure to try the engine out first. Most companies will let you evaluate the engine you free if you want. When using the engines it will become apparent that they are not all equal.

But I do agree, there is a lot of marketing that goes behind selling a few thousand lines of source code for $100,000. I mean, no graphic designer would pay 100k for Photoshop, but we game designers are expected to pay that much for an engine. The market is young though, I have a feeling prices will drop once the industry stabilizes more.

The main things making an engine expensive are in my oppinion:
1 - fame (what games were produced with this engine)
2 - features list
3 - tools / docs / support

1. Fame - It is a very important factor when selling a game engine, marketing.
2. Features list - After all, the engine must be capable of many fancy things.
3. Tools / Docs / Support - for example Unreal3 Engine, has features like any other engine, but what makes it so expensive (besides fame), is the toolchain, many editors, many technologies merged together, from AGEIA to Lipsync technology, and many others, PS3/XBOX support, etc.

But anyway, a game engine is like an operating system, plus, it is a complex architecture that, at a certain point, must work flawlessly, and it must merge several subdomains of programming: graphics, sound, network, AI, GUI, etc., it is not an easy task, and that's why it costs. An engine takes years to develop, just like an operating system, as I always said, the most complex programs: OS-es, compilers and game engines :).

Whoa..
The Unreal engine really costs that much?? :O