Arrows easily break 3 times faster than your bow/xbow, in wich you have invested wpf, and if you use two slots of them... feel the pain...
Also, an Arbalet user consider only taking one slot of steel bolts, since it's indeed pretty long to shoot/move/reload.
And archer with only one slot of bodkin arrows is useless after having shot 17 times (if he heirloomed the arrows), in wich he probably missed 60% of the shots, thanks to the slow missile speed, and less accuracy.
Very well, let's do a comparison of a full loadout then (and as I remember, arrows have a 2x break chance, not 3x)
First, the xbow loadout. This will require a sidearm, and better armor, as it needs to be capable in melee to use that sidearm, and because it can't kite.
Arbalest = 18796
Steel Bolts = 2563
Langes Messer (My personal sidearm when xbowing) = 7517
Armor (my personal set when xbowing)
Chapel De Fer With Aventail = 3112
Heraldic Mail = 4983
Mail Gauntlets = 2074
Mail Chausses = 1290
Total: 40335
Now the archer set, again I'll use the armor I would use for this setup (I'll use 2x bodkins for a full archer set, although I use 1 stack of tatars and a langes messer)
Longbow = 11100
Bodkins x4 (2 sets at double upkeep) = 5058 x4 = 20232
Hammer = 589
Armor
Kettle Hat with Padded Coif = 1480
Peltastos Armor = 1752
Leather Gloves = 92
Rus Cavalry Boots = 412
Total = 35657
Conclusion: The archer set is less expensive.
Now admittedly I'm using a high cost sidearm and decent armor on the arbalest set, but I'm going for the best possible setup for each, and the arbalest set NEEDS melee ability, as it isn't as mobile and can't kite.