Years ago one of my friends asked me to buy him, among other things, a Pentax K-1000. This before the WWW had been invented.
I went through the latest issues of Shutterbug, MP, and PP and listed every offer to sell a K1000 that had a price. Those with no price, just "call," were suspect and rejected. Then I sorted them in increasing order of price and called all who advertised a price no higher than 47th St Camera's. For those of you who don't remember, until they went bankrupt 47th St. was the gold standard of mail order camera dealers, the B&H, if you will, of its day.
Every advertiser whose advertised price was below 47th St's refused to sell at the advertised price. All wanted at least 47th St's price. 47th St honored their advertised price, got the sale.
Nothing much has changed since. The gold standard, these days B&H, advertises real prices, the chiselers who advertise lower prices won't sell at the advertised price.