I engineered a spray system from a bunch of Northern Tool replacement parts - turned out to be about 2/3 the price of buying one of their big agricultural sprayers and parting it out.
One of the items I purchased was a spray nozzle.
When I designed the thing I used their 2009 catalog as a reference - the nozzle in question was a fairly large item, made of metal, and priced at $19.00, which I thought was a bit steep.
When I went online that nozzle wasn't available, and the same part number brought up a cheap plastic part for $7.00. I put all the items in my wish list and came back a couple weeks later to wrap up the buy. I didn't even notice that the $7.00 nozzle was now priced at $19.00 - didn't notice it until I looked at the invoice that came with the parts.
I wrote their customer service and stated my belief that there was a mistake in pricing and their web page history ought to show I was right and I figured they owed me $12.00. After going around three more times it was obvious the customer service guys and marketing guys were just playing dumb to prevent conceding my point.
I've run into that tactic before and it really frosts my a$$. They could have refunded my $12.00 and STILL made the original retail profit on a part which was probably no more than $0.25 to manufacture. Instead they just got greedy.
So, be careful in your dealings with Northern.