Can someone explain the price difference in Trade Chat and Poe.Trade?

Thanks a lot for the useful tips!

I keep them in mind, when I sell stuff. =)

Pricing in PoE is an art more than a science. In fact, there's no science involved whatsoever, but there may be voodoo in there somewhere.

Short version: as stated, trade chat is packed with assbags trying to scam newbies and people who otherwise don't know any better. They're looking to commit crimes, not make sales. poe.trade is an actual, serious marketplace where people are trying to buy and sell items; they price their shit competitively because otherwise someone who DID price their shit competitively will get the sale, instead.

As Cyrano said, the randomized rolls on items can also wildly vary the price. A (unique) item with near rock-bottom rolls for its type can sell for a few chaos, while the same unique item type with perfect or nearly-perfect rolls can often sell for fifty times that, if not more. Legacy items complicate pricing even more. Rare item pricing is a wild jungle tangle of nonsense and tomfuggery that only adept-level sorcerers or better have any remote chance of comprehending.