A Druid's Vestment doesn't take up a body slot and grants one Wild shape more per day. The tables with the wondrous items in the DMG say its price is 3750 gp while the item description says 10000 gp. I also looked in the PFSRD and there both entries say 3750 gp. So what should be the correct price?
Market price for the druid's vestment is 10,000 gp.
The 2012 printing of the Dungeon Master's Guide gives the druid's vestment market price in both table and text as 10,000 gp, unlike the Dungeon Master's Guide (2003), wherein the druid's vestment is listed in the table as having a market price of 3,750 gp but in the text as having a market price of 10,000 gp.
The 2012 printing of the Dungeon Master's Guide is, as of this writing, the latest printing and officially supersedes all others if that sort of thing is important somehow.
Because I started looking through the tables, the Dungeon Master's Guide (2012) deleted the druid's vestment from Table 7–27: Minor Wondrous Items, moving entry 58 to 57, 59 to 58, and so on and making the 100 result Roll Again. The druid's vestment was added to Table 7–28: Medium Wondrous Items at the text's price point of 10,000 gp (the table accommodating the vestment with the deletion of the talisman of the sphere where it was listed in the Dungeon Master's Guide (2003) as having a market price of 9,000 gp but presented on page 209 as a priceless minor artifact). The table adjusted at least one other pricing irregularity as well, that of the necklace of fireballs, type VII (the Dungeon Master's Guide (2012) now listing market price in table and text as 8,700 gp).
All errata for 3.5 can be found here. However, the errata for the Dungeon Master’s Guide does not mention the druid’s vestment specifically. What it does mention is that, if a table does not match the text of an item’s specific entry, you should favor the text (known as “text-trumps-table” in 3.5 circles). Thus, the druid’s vestment officially costs 10,000 gp, which is accurately reflected on Table: Medium Wondrous Items on d20srd.org.
Pathfinder, being a separate game, is free to do things differently; apparently Paizo decided that the 3,750 gp figure was more appropriate for this item. Considering the significant changes to Wild Shape in Pathfinder, however, which make it much weaker than it was in 3.5, it makes sense that it would be much cheaper.