A shop will charge about a buck for a straight gauge spoke. A hub can cost from 20 to .... well, lots of money.
Most shops charge from 50 to 100 to build a wheel.
One option is to lace the wheel yourself and take it to a shop for the final truing and tensioning.
If you do that, then the wheel you will have will be superior in quality to a machine built wheel.
Don't underestimate the quality difference between a hand-built wheel and a machine built wheel. Even if the hand is yours.