LEGO CUUSOO

-The engine is 22 studs long, 10 bricks high, and 8 wide (at the pistons).

-In case you're wondering, I did in fact use the plastic track clips (4x) that hold together straight tracks in a new box of track! They fit snugly inside Technic hollow pins. Two 7 stud half-thick beams to connect the wheels, and two 6 stud half-thick beams to be the piston drivers.

-This model uses modified BBB medium wheels. The 1st modification is for traction: two of the four flanged drivers require a groove roughly 2mm wide&deep. The 2nd (optional) is for the blind drivers in the middle: they must be shaved down to overlap the flanged drivers and also have the axle hole changed to a pin hole.

-Since medium drivers are about 1.5 times larger than standard train wheels, this model goes about 1.5 times faster than normal, and loves to jump...

Picture with all Power Functions elements in place; a 3 x 4 x 4 column of space was dedicated to the placement of all that excess cable...
My main gripe with Power Functions is the amount of real estate the current version of battery box takes up; It would be much more manageable if the dimensions were 4 x 6 x 3.

Just saying...

Cost-wise, this as a set shouldn't be more than $70 USD if and when TLC decides to reproduce it as they're own...
With the minifigure and Power Functions included, there are roughly 260 parts to this engine; The motor, receiver, battery box, light unit, and fig are roughly $50. Then at an average of, let's say, $0.12 per brick for 240 bricks is about $25. Lastly, the medium drivers from Ben are around $20 for a pack of 8 wheels.

So, if you're more of a DIY person, you'd be looking at shelling out around $50 for the parts you don't already have.