This DM wouldn't adjust the cowl of warding
While the Epic Level Handbook on Epic Magic Items does provide a list of "typical characteristics of an epic magic item," and the cowl of warding (Magic of Faerûn 156) (200,800 gp; 0 lbs.) possesses at least one of those characteristics—a market price of just barely greater than 200,000 gp—, on Market Price later says
Use the guidelines for nonepic magic items to determine the market price of an epic magic item, with one addition: If the item gives a bonus beyond the limit allowed in for normal, nonepic magic items, multiply the portion of the market price derived from that characteristic by 10. Some epic characteristics, such as caster level, don’t trigger this multiplier. (124 but emphasis mine)
(For more on epic magic item pricing, see this question and this question.) The cowl doesn't grant a bonus beyond the limit allowed for normal, nonepic magic items. Further, multiple ways exist prior to having access to epic magic items to get freedom of movement, mind blank, and spell turning effects like or better than those provided by the cowl. (How to do that is beyond this answer's scope; you may also be interested in this question and this question.) The cowl, one could argue, simply doesn't meet the guidelines for an epic magic item according to that section on Market Price, despite the cowl's actual, for-reals market price being one of the characteristics typical of an epic magic item.
However, the cowl was published about a year before the Handbook and well before the 3.5 revision, so it's ultimately up to the DM to adjust things if he wants to: The 3.5 revision "is compatible with existing products [like Magic of Faerûn], and these [older] products can be used with the [3.5] revision [of the rules] with only minor adjustments" (Dungeon Master's Guide (2003) 4), and one minor adjustment the DM may want to make may be something like It's epic if its market price is over 200,000 gp.
Before doing that, though, the DM should be aware that the Magic Item Compendium doesn't mention a 200,000 gp market price maximum for magic items other than for armor and shields (6) and for weapons (28), making that guideline unique to (but, to be sure, it really exists in) the Epic Level Handbook. (And it may be time to establish with the group what constitutes a primary source.)
Further, the DM should be aware that in the core rules—that, by the way, electronically includes the epic rules—there's a nonepic magic item that possesses a market price higher than the cowl's market price: the staff of power (DMG 245) (211,000; 4 lbs.). And, outside of core, the staff isn't alone: other high-priced nonepic magic items include the eyes of the spider (City of the Spider Queen 129) (212,000 gp; 0 lbs.); and Keryvian (Player's Guide to Faerûn 121) (207,070 gp; 6 lbs.), the last of the baneblades of Demron; Heartcleaver (ibid.) (314,320 gp; 12 lbs.); the mantle stone of Vhyridaan (123) (232,560 gp; 0 lbs.); and the weirdstone (124–5) (250,000 gp; 0 lbs.). To be clear, these magic items weren't subject to errata and were published after the Handbook then after the 3.5 revision, respectively. Doubtless there are more. (I only made a cursory search.)
With all this in mind and armed with the staff of power and other examples, were this DM to have offered each PC in his campaign any one nonepic magic item, this DM would be fine with a PC getting the cowl as printed in Magic, opting not to make a minor adjustment like adding to its creation prerequisites the feat Craft Epic Wondrous Item.1
Finally, keep in mind that the cowl of warding, although seemingly epic (at least in market price), provides defenses in its freedom of movement and mind blank effects that are pretty much expected of high-level adventurers. High-level adventurers without such defenses tend to find themselves crushed to death or enslaved. In other words, if the campaign continues into high levels, the cowl is potentially among the least abusive magic items available to the PCs because every PC will end up having something like it eventually anyway.
1 The answer to What determines whether an item's epic? is The presence in the magic item's creation prerequisites of at least two item creation feats, the nonepic one and the epic one. (Also see Epic Magic Items on Prerequisites (EL 124).) However, that answer, while accurate, fails to address the date-of-publication issues involved therefore neglects what I think is the underlying question: Should the DM rule that high-priced magic items are actually epic magic items? I'd advise that, based on evidence and experience, the typical DM not to rule that way, but a DM should take into account the players and the campaign before making any ruling.