Unfortunately, mini conifers are the most expensive of the conifers due to how slowly they grow (an inch or less per year). I don't have a clue as to where you would find miniature conifers "cheap".

If you do find mini conifers "cheap", somewhere, there is a big risk that the person selling the plants may not be selling you an actual miniature conifer, but something else entirely.

Your best bet would be to check your local garden centers at the end of the season when many retailers close out their existing stock. You can sometimes find unusual conifers at the big-box stores like Home Depot and Lowes.
Good luck... sorry I couldn't be of more help.
Mike

Here are some mini conifers, fairly cheap ($5 for small pot, $10 for larger one):

http://www.miniplantkingdom.com/search.cgi?searchstring=Conifers&searchfield=aacategory

Of course, not all these will remain small forever -- I'd suggest checking the growth rates on www.conifersociety.org for details. But it's a place to start.

-James

I noticed the minis for the first time last season at some of our better garden centers (www.edelweissnursery.com) for one - unfortunately before my interest in replacing some of my blooming perennials with dwarf conifers was really piqued. Did not look for prices, but I assumed high. And are you sure this is what you're really interested in as opposed to the smaller, slower growing varieties?

I agree with looking to the big boxes and their sales - since their stock changes rapidly, it's not unusual for them to carry some out of the ordinary items - possibly not the niche market minis, but certainly dwarf varieties of many of the evergreens and conifers that you're familiar with. And the prices are more apt not to break the budget.

But as for the minis, I'm thinking if we have them here, they're going to be everywhere. They are tiny (looked at a mugo pine that was hardly bigger than a petunia blossom) and my biggest problem with them would be protecting them from nibbling wildlife, accidentally stepping on them, and planting them where they could actually be seen and enjoyed.