16 CFR § 233.2 - Retail price comparisons; comparable value comparisons.
(a) Another commonly used form of bargain advertising is to offer goods at prices lower than those being charged by others for the same merchandise in the advertiser's trade area (the area in which he does business). This may be done either on a temporary or a permanent basis, but in either case the advertised higher price must be based upon fact, and not be fictitious or misleading. Whenever an advertiser represents that he is selling below the prices being charged in his area for a particular article, he should be reasonably certain that the higher price he advertises does not appreciably exceed the price at which substantial sales of the article are being made in the area - that is, a sufficient number of sales so that a consumer would consider a reduction from the price to represent a genuine bargain or saving. Expressed another way, if a number of the principal retail outlets in the area are regularly selling Brand X fountain pens at $10, it is not dishonest for retailer Doe to advertise: “Brand X Pens, Price Elsewhere $10, Our Price $7.50”.
(b) The following example, however, illustrates a misleading use of this advertising technique. Retailer Doe advertises Brand X pens as having a “Retail Value $15.00, My Price $7.50,” when the fact is that only a few small suburban outlets in the area charge $15. All of the larger outlets located in and around the main shopping areas charge $7.50, or slightly more or less. The advertisement here would be deceptive, since the price charged by the small suburban outlets would have no real significance to Doe's customers, to whom the advertisement of “Retail Value $15.00” would suggest a prevailing, and not merely an isolated and unrepresentative, price in the area in which they shop.
(c) A closely related form of bargain advertising is to offer a reduction from the prices being charged either by the advertiser or by others in the advertiser's trade area for other merchandise of like grade and quality - in other words, comparable or competing merchandise - to that being advertised. Such advertising can serve a useful and legitimate purpose when it is made clear to the consumer that a comparison is being made with other merchandise and the other merchandise is, in fact, of essentially similar quality and obtainable in the area. The advertiser should, however, be reasonably certain, just as in the case of comparisons involving the same merchandise, that the price advertised as being the price of comparable merchandise does not exceed the price at which such merchandise is being offered by representative retail outlets in the area. For example, retailer Doe advertises Brand X pen as having “Comparable Value $15.00”. Unless a reasonable number of the principal outlets in the area are offering Brand Y, an essentially similar pen, for that price, this advertisement would be deceptive. [Guide II]