Sandals have long been a favored fashion accessory in UO. Price depends on rarity, hue, and source (holiday event, bug, pre-patch).
Christmas sandals were made available during the 2013 Christmas event, and cost 500 holiday coins. Players got a randomly-chosen color from either one of two blue sandals, red sandals, or white sandals. Their hues are 8, 108, 33, 133, 1150, and 1154.
Holiday sandals average price: 2.5M
Leprechaun sandals were made available during the 2013 and 2014 St. Patricks Day event. Each year offered different colors. They were found as loot on leprechauns. Their hues are 272, 273, 274, 573, 669, 670, 672, 673, 674.
Leprechaun sandals average price: 800k
Bulk Order Deed Sandals
Bulk order deed sandals are available as a reward for turning in certain bulk order deeds. Their hues are 1, 901, 902, 911, 916, 1156, 1175, and 1235. The hue 1 sandals (true black) are the most valuable.
BOD sandals average price: 5k
Black sandals average price: 40k
Anniversary sandals were given out randomly during the first and second anniversary celebrations. Their hues are 71, 1271, and 1274 for First Anniversary, and 1159 and 1359 for Second Anniversary.
Anniversary sandals average price: 2.5M
Cupid's sandals were made available as prizes for killing Cupid during the 2013 and 2014 Valentine's Day events. Their hues are 21, 22, 25, 26, 31, 233 333, and 433.
Cupid sandals average price: 800k
Vendor Sandals are available from killing vendors. Some vendor sandals were dyed pre-patch and thus their hue and naming is relatively rare.
Vendor sandals average price: unknown