Allen - Let me add some additional background to the above posts in the way of clarification.
First off, there are very few true "swap meets" to be found in our hobby today, ones where attendees honestly swap an item of theirs for one owned by another, with or without actual money changing hands. These sorts of meets did exist in the hobby's distant past but are very few and far between these days.
Today there are mainly "train shows", which in most cases might be considered more akin to mobile hobby shops. In some areas of the country these shows will include a modest selection of older, or used, cars, locomotives, etc., while in other regions they are dominated by sellers offering mostly brand new items.
As to obtaining bargains at shows, that situation is equally highly dependent on one's particular location and luck. Here in the Northeast one use to be able to regularly find a whole host of bargains at train shows (back in the 70's and 80's). Since the mid 90's, however, many of the shows have folded and those that remain are mostly far less favorable to bargain hunters, with newer items (which are decidedly in the majority) offered at list, or even above and dealers unwilling to negotiate price. You will also encounter some dealers who feel that older car and structure kits are somehow "collectible" and adjust their prices accordingly. In coming months it will be interesting to see just how the now OOP Athearn Blue Box kits are priced, for example.
If you are looking for a pleasant Sunday afternoon out, are new to the hobby and enjoy looking around at tables full of items and perhaps some display layouts, then you'll likely enjoy train shows. On the other hand, if your main thrust is a search for particular older items, especially in any volume and at bargain prices, I'd tend to stick with eBay.