Leadwerks Game engine is basically a poor mans Unreal Engine. The difference? Once you pay for Leadwerks Engine, the games you make are 100% yours to sell, no royalties owed to Leadwerks. Unreal Engine will start taking and keep taking a cut from $50k upwards.
Not the cheapest price it has been ($14.99, 5 months ago), but still a fairly good price for a "drive away no more to pay" type engine. The RRP for each item is $99usd. Buying both the Engine and the Professional DLC comes to roughly $50usd today, as opposed to the regular price equating roughly $250aud. I'm all for being fluent in as many engines as possible, you never know what software a studio will choose to use in a collaborative effort.
The Professional Edition allows you to break out of the confines of the engine and use your own C++ code. An assets store is attached and available to buy and sell assets just like Unreal, and it has Steam integration, so you can upload and share your games and assets to the Steam Workshop.