Is my tax preparer overcharging me?

We've gone to the same preparer for 5 years. It's actually my husbands friends parents company. Last year we paid $170 for fed, state, education credit(1098t), city earning tax. Along with all of our forms we also sent them a print out of his account details from my husbands schooling. After filing our taxes I decided to double check the work and I discovered the amounts on the 1098t did not match the account details. So we had to get 2014 amended with this years. This year we added a form because my husband now works in a different state and we also bought a house. We sent them the account details again this year. After we receive the email to review and sign for our taxes I noticed they didn't include the education credit. I called and was told its because the 1098t showed we basically got $2000 extra in scholarships and grants, we did not. So I went over the account details and again, the 1098t was wrong! We got the new 1098t and they revised our taxes. They emailed us the invoice which was $395! I feel we were already paying them for a service which they failed to find an error on one of our forms. Is that not why we pay a tax professional to do our taxes?! If I didn't catch these errors we would have missed out on $1700 in returns. There's been something wrong on our last 3 returns that I've caught. Being my husbands friends parents, I wanted to give them the benefit of the doubt. She claims it's because the earnings tax was for half a year so the calculations took longer, she had to email my husband a few times for school receipts, and other forms took an hour and a half to do. She was pretty vague about the charges and when I tried to ask a question I was interrupted by her saying "I already told you the extra costs". Now if they would have caught the error in the papers we sent them, I would be more understanding at a larger increase. I don't even think they went over anything. It's like they just used copy and paste on our forms. Am I crazy for thinking they are ripping us off?