I was recently asked if a Chateauneuf-du-pape reduced from €30 to €15 in a Supermarket chain was a good wine. Aside from the fact that no-one in the Wine business has that sort of margin and below cost selling of alcohol is now illegal, we generally just say 'try it, and if it's worth €15 then it's good - but it was probably never worth €30'
On another occasion, I noticed a big display of a good Italian being built in a (different) Supermarket and asked for the price. '€24 a bottle but wait til next week when it's on Special at €16' was the reply, even though it was in my local Off-Licence at €16.99 with case discounts if required!
A friend in the Electronics business once told me that they run Price Guarantee Offers all the time, but the customer can't win. One business sells Model 123XLa and the competitor sells the exact same product but it's flagged as Model 123XLz! So not the same!
There is definitely a good bit of Marking Up to Discount Down going on, but it can be hard to spot.
So just remember, If it looks too good to be true, it probably is!