To 'set someone back' is a phrasal verb meaning to delay the progress of someone or something. If you set someone back you may, in fact, cause them to regress in some way or cause them to run late or behind schedule. 

1. The machine breaking down set us back a week and has meant that we won't be able to get the order completed before the deadline.
2. Not getting the contract is a setback, but we need to just roll with the punches and look forward.
3. You may think that other people have more experience than you but you shouldn't let that set you back. You should still go for that promotion.

1. I had planned to get to the east coast by Friday, but my car breaking down has set me back about two days.
2. We need to raise 5,000 by the end of the month, we can't afford anything setting us back.

You can say 'how much did that set you back?' when you are talking about money or how much something cost. 

1. I love your new car! How much did that set you back?
2. Our new kitchen set us back quite a bit, but I think it was worth the money.

1. The product I'm selling is not only versatile and effective, but it's also very affordable as it will only set you back £10.
2. Parents are complaining that the cost of uniforms and schoolbooks is setting them back too much money at the beginning of the school year.