It depends on the stats of the dread.
Blaze cu's I've been seeing selling at ~350-600m lately.
Post the stats of the dread so we can get a better idea of it's worth, I know a few people who have dreads valued at ~1b. Like I said though, it's all in the stats, essentially you'd be trading a something utilized primarily for PvP for a novelty pet/trophy. Unless you're looking for a pvp capable blaze (which I know of only one, which is stam bugged and is valued at 5b)