The feats required to use a legacy items are bonus feats, granted to the wielder as soon as a given ritual is completed. There isn't a feat cost associated with legacy items (despite the misinformation in this thread).
Just for curiosity's sake, I selected one legacy weapon more or less at random, for a comparison with crafting. I picked Durindana, Weapons of Legacy p. 75.
Final abilities: +4 holy undead bane longsword (98,000 gp), Saint's Grace [+2 resistance bonus to saves] (4,000 gp), Endure Evil [continuous protection from evil] (2,000 gp), Pelor's Gaze [daylight, 1/day)] (5,400 gp), Pelor's Baleful Eye [+4 levels for Turn Undead] (10,000 gp, conservatively?), Pelor's Protecting Grasp [death ward, 1/day] (10,080 gp), Hallowed Ground [hallow plus daylight, 1/day] (18,360 gp), Pelor's Dazzling Beneficence [total concealment for 15 rounds, c.f. displacement, 1/day] (16,200 gp).
Total Market Value (note that this ignores the x2 modifier for slotless items and the x1.5 modifier for multiple abilities): 164,040 gp.
Cost to Craft: 82,020 gp, 6560 xp, and Craft Magic Arms and Armor.
Cost as Item of Legacy: 55,200 gp, -2 to attacks, -3 to saves, 14 HP.
The cost of the item is high, but it's not as ridiculous as people are making it sound. The biggest drawback, as someone has alluded to, is that this weapon simply isn't powerful enough for a 20th level character, and (as far as I can remember) there aren't any rules for how you independently improve a legacy item.