My right rear brake drum seized on my 2006 Dodge neon. The left side was dragging but didn't seize. The parking brake cable froze up causing the e brake to not disengage. The shop owner said there was extensive "bluing " which was expected since the brake drum got really hot. Now a year ago or so my dad and I purchased a full kit for both sides i.e. new drums, shoes, hardware and master cylinder and got out the door for about $100 total both sides.
Unfortunately the shop owner probably picked up on multiple warning signs.
1. This is basically a "come back" on a DIY repair. He has to assume that because something went wrong, there may be other problems too (stripped or missing fasteners, air in the lines, assembled incorrectly breaking other things, etc.)
2. E-brake cables are notoriously difficult to replace when there's any rust on the undercarriage. The little clips and clamps break off and have to be drilled and tapped. The cables often run over, around, or behind all sorts of suspension bits and even fuel lines.
3. Disassembly of the center console on older vehicles (this one's 17 years old, right?) is fraught with peril. The plastics are extremely brittle and the rubber parts are usually disintegrating. Not to mention there's usually gross old food and other crap in there.
4. Once you get the console apart without breaking it, getting the cables threaded through the floor and into place is also physically challenging for the mechanic. It involves a lot of contortionist antics and often two people, one under and one inside the vehicle.
5. Once it's all back together, he should insist on full brake fluid flush after any sort of brake overheating.
6. The shoes and cables almost always requires a test drive, then putting it back up in the air to do a final adjustment, then another test drive.
Even after all this is successfully completed, there's still a good chance the customer brings it back because of noise or it doesn't feel right.
I'm not saying the quote is reasonable, or that you did anything wrong, just that there's more to me it than a pile of parts.