I had a new wheel on a new bike that didn't have enough grease and it went bad.
Having caught it relatively early I was able to save the races. The bearings were a couple of pounds for 100 on amazon.
Changing bearings is not complicated or time consuming.
If you have cartridge bearings - I have got loads more life out of a siezed bearing by removing the dust cover, cleaning it thoroughly and regreasing. Zero cost, except time.
Chainrings I have bought from amazon loads if times. I have even set up email alerts through 3rd party sites to keep an eye on the price and get alerted for price drops which amazon do all the time.
The shop has overheads and will be looking out for themselves, just like a car garage.
You can do this work yourself and save a lot of money or let them sell you a bike.
Your call.