I am not a legal professional, either, although I do have a law degree (JD). What you are suggesting is right on point. And that is, that the “victim”, here, “relied upon” the advice of the seller, who held themselves out as “experts”. It may not be “fraud”, exactly as fraud includes the element of “intent to defraud”, which may not be the case here. For there to be fraud, the seller had to have intentionally switched out the correct lens with the replacement lens — for whatever reason — figuring that the customer would not know or care. It’s a matter of whether or not there was “full disclosure”. If the seller said, “We don’t have the 16-80, but we have the 16-85, which will work just as well for you”, fine, no problem, but there should have been a price adjustment or some other similar compensation.

This was also a “contract”, of sorts. If “fraud” was involved, the aggrieved party has the right to rescind the contract. Return the product(s) and receive a full refund. If “fraud” was NOT the case, here, the seller should be given the opportunity to “cure”, or to make good on the “contract”.

I am like a lot of you, retired. Have been a serious hobbyist photographer sing the early 60s. I have been reading UHH for some time now and have great respect for several of you regulars and not so much for a few others.
I decided that I needed to join UHH so I could chime in on rmalarz’s excellent series of posts on Exposure and How It Works - A Beginner's Guide. The water flow model is right on and should give the beginner a good “feel” of what is going on.
It is however missing one piece. The flow of water through the opening is a function of the pressure of the water the valve is holding back. The higher the pressure, more water will flow through the aperture in a given time. If you have an opening and time that just fill the glass, it won’t be the same if the water pressure changes.
The water pressure is the equivalent of how much light is on the subject. The pressure gauge on the water supply is equivalent to the photographer’s light meter. The shutter speed and aperture vary based on the brightness (pressure) of the subject.
Now for some comments not based on rmalarz’s posts.
It’s a funny triangle that has four sides. The exposure triangle looks at the three controls in the camera; aperture, shutter speed, and ISO. The fourth side and every bit a significant is the amount of light on the subject. Sometime the photographer can control this, sometimes not.
I’ve always like to think of it as 1) How much light do we have (light meter reading), 2) How much light do we need (ISO), 3) what combination of shutter speed and aperture will give the correct exposure (and have the best side effects, motion stopping and DOF) The old fashion light meters made this easy since when you dialed in the ISO and Light reading they showed all of shutter speed, f stop combinations that worked. You could just look and see them, you didn’t need to do the mental calculations. Once you had taken a few thousand pictures the calculation became second nature, but seeing it really helped the novices. With meters built in the cameras you only see what is correct, not as helpful for learning.
If you don’t like the options, change something (put more or less light on the subject, change the ISO). Don’t forget the fourth side of the triangle, use a flash, use a reflector, move the subject closer to the window, get the light source behind you,