Compared to what?  This hobby is no different than life.  Some cars are less expensive than others.  Some houses are cheaper than others.

People pay $3.00 for a gallon of gas, and cry.  They pay $4.00 for a cup of coffee and it's a bargain.

This is another pointless waste of electrons.

Short answer without editorial comment.
Bachmann stuff runs on 45 mm track.  Any 45 mm track that's commercially available down to about code 215 (maybe smaller but I can't vouch for it, and I won't condemn anyone who has).

It's wise to not leave anything with motors and gears outside all year.  Not mandatory, and some folks with mild climates can get away with it.  I live in Sacramento, and won't leave my engines outside.

I do leave some of my less expensive (read Bachmann) cars out because I like to see equipment on the road.  You don't have to.

My buildings I leave out year 'round, and have to repair or rebuild them every three or four years.  Your mileage may vary because of your climate.

People and cars come in (sometimes at the end of a session).  Critters and others like to pick them up and scatter them.  One spring I brought in die-cast cars I'd forgotten about under a pile of leaves.  Had to take the completely apart and wash them in hot soapy water (and dry them thoroughly before reassembly).  Not leaving them outdoors is a really good idea!  Now I found out.

No No NO!  There is nothing wrong with track power and aluminum.  I can't figure out why -- with so many experts around -- everyone seems to miss the fact that aluminum is the second best conductor of electricity after ... copper!

Many homes are wired with aluminum, and their lights still work!

Many modelers in my area use aluminum and track power because it has been cheaper to buy, the smaller size (Code 250 and 215) is more like real (without becoming a rivet counter).

It has it's drawbacks, but not because it's aluminum.  It's not as robust as brass and may deform if you step on it.  It can't be soldered very easily.  I've had some of my shorter pieces welded together.  It needs to be cleaned, but it's always worth a walk around the layout to check for twigs and other debris.  I just do it pushing a wall sander.

Write to me off line if you really want to know how I feed about aluminum.  I've used Llagas Creek track, rail, and switches and have been satisfied by all of them.

If you'd like to see some of the track, you can see some of my pictures on flickr as train44buff.

I bought the Sam's set last Christmas.  Nice pairing of passenger cars and trolley.  Then I bought a Christmas Combine on evilbay.  Threw the track into a bin to use for indoor storage, and put the power pack aside for when I need a spare on my workbench.

Then I rolled up my sleeves.  Although the box said the cars were lighted, they weren't.  No battery boxes, no lighting, no wiring.

No problem.  I installed metal wheels and LGB power pickups in one of the trucks, and converted all three to LED lights.  I connected the cars with plug in wires that look at first glance like mu cables.  Paint the roofs a dark color to prevent the light from leaking through the plastic!

Next, replace all wheels with San-Val wheels so all my pax cars are the same height. Then I put kadee's on all cars and both the tender and the front pilot.  (VERY simple on the pilot, just take the dummy out and install an 820 in the pocket!

While I had the cars apart to install the lights, I removed the screws holding the roofs to the car bodies, and installe brass pins from the outside.  Now I can get into the cars without disassembling them.

lastly, I noticed that there was no glazing in the end doors of ANY of the J&S cars, not the Christmas ones, not the old Bachmann kits, nor the ready to run ones I'd purchased.  So a little band saw work on some old kitchen light panels, and all my cars have glazed windows.

What would make those cars OUTSTANDING would be the new metal hand rails Bachman is putting on their newest cars.  There are photos of a Christmas car with the LED lighting and shot of other converted J&S cars on my flickr page.  Train44buff

Several have commented about the lack of pulling power.  I agree.  Mine will pull two cars if I'm lucky.  I've got about eight J&S cars that sit on sidings because of that.

What is the solution for someone who's not into major engine surgery?