My cello bow cost $300 and it's not very special. My cello costs $2500 new and it's rather crappy. Whereas my teacher plays a $30,000 cello using a $3500 bow.
WRT the instruments the cost is greatly influenced by the wood used, the cut of the wood and the skill of the luthier. Case and point, my cello uses beautiful flame spruce wood for the back and sides
but the top is a cheaper cut, is very thin and prone to cracking, the bass bar and sound post are made of crap wood, the finger board is very thin and not made of ebony, the tail is metal and the scroll is mass produced. The joinery is really poor and prone to separation. So yeah you do get what you pay for.