When I'm bidding on items on eBay, I pay attention to the shipping costs for that item.  Sometimes shipping costs can add $10 to $12 dollars to the item cost making it less attractive, especially if the winning bid will be about the same value.  I have even avoided bidding on some items when I've found a similar item with a smaller shipping cost.  Although I'm not a major buyer or shipper of model trains, I believe I've found some simple, inexpensive, and mostly free ways to ship your items.  In addition to being very inexpensive, your shipped items appear professionally done, adding to your credibility as a seller.  What I describe is a system via the US Post Office using Priority Mail.

What you need:

Boxes - The post office actually give away two sizes of boxes under its Priority Mail system.  The boxes can be obtained from your Post Office or may be ordered in lots of 25 from the US Post Office web site.  There is absolutely no cost as even shipping is free.  The down side, there are only two sizes and the boxes are not supposed to be used for other purposes.

Shipping supplies - This would be a postal scale (5lbs max), packing tape, bubble wrap, and styrofoam peanuts.  These are items you may have to purchase, but I've found that bubble wrap and styrofoam peanuts can be had for nothing.  I work in a large building that receives many packages.  The styrofoam peanuts are removed from the box and stored in a bin.  For the price of getting them myself, I have obtained several garbage bags of peanuts for nothing.  Bubble wrap can be recycled from other packages, but investing in a roll pays big dividends.  The tape should be package tape and can be reenforced with fibers, but this is not necessary.  I like the clear version for reasons stated later.  I actually bought a dispenser from Office Depot and get large rolls in a six pack from most office supply houses.  Although you can go to the Post Office or other places to weight packages, dial scales up to 5 lbs max are inexpensive and save the time of seeking a scale elsewhere.

An account on the US Post Office web site - Although you can go to the Post Office and purchase postage, using the Post Office web site saves lots of time standing in line.  You can pay for postage, print labels, and even call for home pickup by your carrier.  You can purchase peel-and-stick labels, but I simply printed the shipping label with postage on plain paper, cut out the label, and stuck it on with some clear shipping tape.  As a plus, you can provide the receiver's e-mail address and they get notice of shippment - and both of you get the tracking feature free (a $1.00 or so value).  The down side is you must be willing to use a credit card or debit card to purchase postage.

Use Priority Mail - Although the Post Office offers other forms of shipping, Priority Mail is the better option.  Priority Mail arrives in 2 to 3 business days.  I have waited almost 4 weeks for Parcel Post shippments.  The cost is similar to other carriers.  Don't use Express Mail as it is more expensive and has limitations.

The up side is you get a box that doesn't look like it's built from recycled pieces, safe and secure packaging, a professional looking label with postage, and the convenience of doing from your own location.  The down side is the need to use the Post Office as your shipper.