I'm a bit of an art collector. Your links are dead so I can't comment specifically, but in general:
This value is going to depend very heavily on whether there's an active secondary market for the artist. To determine whether there's an active market, check ebay to see if there's bidding on other prints by the artist. If not, do a general google search and see if the artist is being discussed/traded in any forums. They might turn up on collector's sites like expressobeans.com depending on the genre.
If you determine that there is an active secondary market, your best bet is to sell them on ebay. You'll get the widest exposure to collectors around the globe. If the artist is popular on a collector's forum, you'll want to alert them to your ebay posting.
If there's not an active secondary market (much more likely), your best bet is to post them on craigslist and hope someone takes a shining to them. With no active collectors, they're likely to languish on ebay (they might not sell for $1) unless the subject matter is of specific interest to someone. You might have to post them a few times and/or adjust the price on CL to generate interest. Feel free to post the retail prices and links since "$400 of prints for $50" can be an effective sales pitch. Unfortunately, without an active secondary market, you're going to have to pull a starting number out of thin air. You'll want to go high enough to make it worth your while and leave some room for negotiation, but not so high that you're going to scare away all potential buyers.
In the large majority of cases, the "limited edition" factor is meaningless. There are literally millions of limited edition series out there, the vast majority of which are worth little to nothing. For highly collectible artists, a small edition size will often be more valuable than a large edition or an open edition, but that's probably true of less than 1 in 500 artists.