Well since you were honest about things I will offer you some tips.
1. Ask for all of the old parts back. All of it, resell it here/Craigs List/Kijiji/Ebay to recover some of your costs. Those old parts belong to you now once you pay for it.
2. Go on Ebay and look for the OEM plastics, you can get them cheap. Do not buy from a dealership.
You might be able to find them locally from racers as well, check cherrypicker.com
3. Post a closer shot of the estimate bill. I would like to see the prices you got quoted or type it in
4. Why is there rust on the bar ends for something that just happened?
5. You can get bar ends and stock levers shipped via ebay for probably less than $50 probably $25.
You do not have to replace with brand new items because the bike is used and has a depreciated value.
You have to put it back in the state it was in before you hit it meaning used parts that are clean/newish looking can do the job.
Find out what that bike sells for, look online to get ideas.
Contact Dave at Competition Cycle on this forum, he likely has all the parts you need and can do the install as well.
Good luck!
Did he park the bike directly behind you in your parking spot?
He might have some fault in this depending on where he parked and the spot your car was in e.g. if private parking spot and he placed the bike within your lines then he might have some fault as well (just speculation).
From what I see he should be able to replace the items himself in about 2 hours.
Tell him and write it up that you pay him $1500 and call it a day.
That bike can be fixed back for $500 from the pics you posted and info you have provided thus far.
* Again, kudos to you for doing the right thing and coming here to ask for advice.