Strictly a matter of opinion but another great choice of crossbow for THF is Velocity Bow +1. Although it lacks the ranged accuracy and lower base damage, it quickly makes up for it in AGI bonuses (Trick Attack, minor r.acc and evasion/parry) and one of the if not the lowest delay for crossbows thief can use. Great for getting a quick shot off for bloody bolts in a tight situation when time is of the essence.
Ranged accuracy is typically cheap and in plentiful supplies for thief. I rather not blow 1 mil on this when it can be made up for via Ohat, Pahluwan body, Deadeye Gloves, Behemoth rings, Precise Belt, etc.
I see many people here say that this isn't necessary cause you can get the racc in other slots. Those people seem to only use Thief to farm some low level mobs. THF has rather low Marksmanship skill (75 cap being 230). My racc set is nearly perfect with +65 acc in gear and AGI+41, and even with sushi I still miss a lot on important stuff.
Again, if you're just farming, yea, there's cheaper alternatives, but for anything that's a challenge (like getting Acid Bolts on Salvage bosses or lowmanning some HNMs), you will need every bit of racc you can find. And this piece is godly for that.
Also, it will save you a lot of money in bolts, cause you won't need half a stack of acids just to get the DEF down on.