No, it is NOT!
This bloke is happy to pay for 144 to be printed, at the 144 price break. He just has only 126 substrates for it to go onto, instead of 144 of them.
The original poster is happy to pay for 144 prints, though he has a shortfall of substrates.
The real problem is simply that they didn't discuss all of this FIRST.
Oops, upon further thought... the supplier's formulas are flawed. There is an OVERLAP in his price structure, which shouldn't be there. To the OP, you might suggest to the supplier to draw a graph of their prices/qty and see the overlap. A visual might be easier than explaining with words.
On the other hand, other people's comments are still valid - you knew the price, so it's not really a rip off in that sense as well. It's quite simply, a poorly structured scale - to which you have discovered the loophole - which they should have done long ago.
It's like saying if you buy 12 apples i'll sell em to you for $1 each, but if you buy 13, it's $11...
You may find yourself in a similar dilemma at a fast food chain, asking for a large burger meal - but saying that you won't eat all the fries so they can just make that a small but you're happy with the rest. I can only imagine the time consuming discussion which would ensue with management and the 15 year old behind the counter.