are alterations really this expensive?

I had mine done through the bridal shop that I bought my dress at. It was a flat rate of $350 which included the bustle, hemming and any other needed alterations (taking in or letting out). She had to remove the lace and beaded trim, shorten multiple layers, hand sew it all back on, take in the sides along my waist and hips and I had a 13 point bustle (it was a complicated, side swept train. I honestly had no idea how one even could bustle it but I love my bustle so much). From comparisons out here that was a steal so it sounds to me like you are getting a good deal but maybe getting a couple other quotes to double check wouldn't hurt.

One big reason why i made my own dress. since I was having a terrible time making up my mind on what I wanted, a few times I did go shopping- I saw a list in the dressing room on how much alterations cost. after realizing very quickly that alterations alone that I'm sure they would insist on doing would be far more than my making my dress out of silk I was saving, made my decision much easier.

that and I realized I'd like a simple dress of silk that I made better than what i could buy

but yes, alterations are expensive.

Get another quote, this is too high IMO.

That seems about right, my alterations were a whopping $665 didnt even include a bustle (which i didnt need)

just some taking in of my dress so that it fits my body like a glove.

$300 sounds good in my opinion.

Never hurts to get a 2nd opinion. I paid $405 and had the bust slightly lifted, detachable cap sleeves adjusted, taken in from waist to thigh, back let out a hair, slip/petticoat sewn in, and bustle.

Wow all of this makes me so grateful for my seamstress - I paid $75 for a hem, six point bustle, cups, and taking it in at the bust