I have found that it is spotty. Some thngs went up and other things dropped. The Bio bug kllled the price of Mutagenic Paste although over the last few days it is starting to come back. I am selling a ton of crafted gear in addition to my usual mats and making a ton of credits from them. I never bothered with that before the f2p hit.
I think that all in all prices have actually increased. I am on Harbinger and deal in mats at all levels and from all crew skills.
I have seen a lot of crazy low listings (your ballpark) where I have bought and relisted and made a killing as well.
As far as people listing one item at a time, I just ignore them and page through the first few pages of listings. I can't comprehend why (especially with the limited GTN interface) anyone would take the timee to list one item at a time, but to each their own. LOL, they will never make a million credits one listing at a time.
you are right, somethings have gone up but used to be staples of selling for 1200cpu like polyplast and electrum now sell for 650-800cpu range