Welcome to ATP, Miss Jeri!
The Classifieds and Group Buys forum sometimes has "group buys" listed.
That's where one member arranges to make a bulk purchase from some vendor that only sells a whole tray-full, or dozens, of one kind of seedling at a time. They get together a group of people, each of whom signs up for a few plants. then they get a big discount for making the large order, but the organizer has to divide and ship plants all over the country.
The seed and plant swaps are great ways to get a big variety of seeds or plants from other members, if you have some of your own to offer. You don't need to arrange one-to-one trades in those swaps, just have to offer some things that match the theme of the swap and that others are likely to want. Then you just pay postage for two boxes: send your stuff TO the organizer, and then send everything you asked for, back to you.