Yes, True Love Locket is functionally identical to a Penta-Heart Pendant. The former existed in the game for a long time before the latter was introduced (when PvP was introduced I think). You can learn more by reading their wiki pages. True Love Locket is much, much harder to get. So it is able to demand a high price, from players who want to own obscure items.

To get price checks on items, you want to post in the Bazaar forum. The people there can give you good information. So please move this thread there (by editing the original post and choosing that forum from the drop-down menu).