Could be stock on the shelf vs just reordered by the company. The supply chains were disrupted by COVID and now by COVID in China which shut down factories and ports. When materials are in short supply and shipping and manufacturing costs go up restocking prices go up... then prices to the public.
You were lucky to get the older stock with the lower price. Indeed it pays to shop.
"Amazon was once the place to go to for the best deals...not anymore though." In total agreement with this. If you buy groceries like I do perhaps you have noticed that the prices are higher on a weekly basis.
... in this case at Adorama. That is unless I'm reading something wrong.
Epson T850 Ultrachrome HD Ink Bundle, for SureColor P800, $1098.00
Amazon has them priced at $779.00
I just ordered them from B&H for $559.00
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Pricing can be extremely complicated. There are so many variables that we can't even begin to make sense of it. As NMGal said, it pays to shop around. Before I buy something, I do a search: "XX for sale." Of course, a low price alone isn't enough to sway me. Who is selling, and how much is shipping?
I went back and looked a little closer. The picture showed 1 each. Next to it it said kit. Clicking on the word it showed a list of all the colors and said (2) next to each one. Seems like that should have been right out in front.