I would agree there are shops out there that want to make money, and the bottom line is all that is important to there shop and pocket book.
I have a honey comb style rad, I had it boiled out at a rad shop for $25.00, this type of rad cannot be rodded out, so if there is any coating in the zigzag portion of the honey comb core, it is very difficult to clean out. Mine came back pretty darn clean, with good flow, it wasn't all that dirty to begin with.
I had a rad from a 1951 Dodge for a while in my 47 Chrysler, it is a tube and fin design, and is pressurized at 4 lbs. This rad was filthy,leaking and was not cooling worth as $hit.Most shops only wanted to re-core it at $350.00, I found one shop they did the rodding, cleaning and solder repair for around the $100 mark, I shipped this rad to Norway to a member of this forum, it is working good.
Last summer at work, we have a couple of 2 ton trucks that were both 1980s and would boil over immediately upon driving a few miles.Both rads were recored, this brought the coolant temps to normal for both trucks.
So sometimes a repair and/or cleaning can be done, other times a re-coring is necessary.
I have a rad from my 47 Chrsyler parts car, I am going to have it re-cored, it will be $400.00, but the cooling will be great.............Fred