6lb of LME costs about 27,00$CAD, which is about 20,17$USD. Add a few bucks of hops and some yeast, and you've got a decent brew totaling something around 25$USD or so.
I was seriously considering going all grain, for some time, but I started trying to brew without boiling it, and so far, so good, and if that keeps up, I'll just ditch the all-grain project completely. Foregoing kits, picking LME and hops already gives a lot of flexibility in recipe making. At most, adding a partial-mash with specialty grains allows a bit more, without needing as much fuss. Heck, they can be cold-steeped, possibly avoiding boiling altogether, or at most boiled in smaller volumes with the bittering hops (despite the lower effectiveness this is likely to cause).
Also, of course transitioning to something is gonna be cheap if you already own everything. But that's fudging the numbers, in reality, it's not free, you just already happened to have paid for it. For example, I could say my whole brewing setup was free! I didn't need to spend a penny when I started making beer despite my 50 gallon or so capacity! But in reality, I've been brewing mead for a while, so I just already had a ton of stuff. No kettles, though, or anything relating to boiling. So no heat-able pump, no valves, no chiller of any sort, no false bottom, etc.
In reality, someone can brew complex recipes with just simple food-grade plastic pails, a few feet of tubing, some recycled bottles, caps, and a small kettle. For the cost of the LME+hops+yeast+adjuncts. While on the other hand, I don't see many people doing all-grain who don't have multiple large kettles, something for the sparge, heat-tolerant pumps, chillers, fairly efficient filtration equipment, lots of tubing, lots of valves, temperature monitoring and control, burners (typically propane), etc., etc., etc.
Obviously if you already have all that, the incentive to switch to all grain is greater.
But the main cost saver is simply to avoid kits, and to make one's own recipe, especially if you can bulk-size your ingredient purchases. Avoiding frivolously premium ingredients, such as patented hops, can also help save a few bucks off every brew.