I like Pringles as much as the next person, especially since they have been releasing new flavors. However, here is some food for thought.
In 2007-09, Proctor & Gamble (P&G), the manufacturer of Pringles, was in tax dispute with the U.K. government. P&G contested the claim that Pringles were "made from the potato" and thus subject to a 17.5% VAT. See VAT Act 1994, Schedule 8, Group 1, Excepted Item 5.
Any of the following when packaged for human consumption without further preparation, namely, potato crisps, potato sticks, potato puffs, and similar products made from the potato, or from potato flour, or from potato starch, and savoury food products obtained by the swelling of cereals or cereal products; and salted or roasted nuts other than nuts in shell.
If P&G won the challenge, then Pringles would be treated like other food items and not subject to VAT. See VAT Act 1994, Schedule 8, Group 1, General Item 1. Thus, P&G and its customers would save millions in taxes.
On May 23, 2007, the VAT & Duties Tribunal determined that Pringles were "made from the potato" and thus subject to a 17.5% VAT rate. See Proctor & Gamble (UK) v. The Commissioners For Her Majesty's Revenue & Customs,  EWHC 1558 (Ch) at ¶ 1.
P&G appealed to the High Court. The High Court disagreed with the Tribunal and found that for a potato product to be "made from the potato" it must be "wholly, or substantially wholly, made from the potato". See Proctor & Gamble (UK) v. The Commissioners For Her Majesty's Revenue & Customs,  EWHC 1558 (Ch) at ¶¶ 58, 79. Given this interpretation, the High Court found that "Regular Pringles are not made from the potato, potato flour or potato starch so as to fall within excepted item 5". See id. at ¶ 86.
Interestingly, P&G stated in support of a different argument that "[t]he percentage of potato varies [in a Pringle]: at the time of the hearing it was about 39.48%, today it is around 42.2% though it may drop again in 2008 to 35% to 38%." See id. at ¶ 106. Additionally, , P&G stated that the fat content of a Pringle is approximately 33%. See id. at Annex, ¶ 2.
In May 2009, the Court of Appeals reversed the lower court. See The Commissioners For Her Majesty's Revenue & Customs v. Proctor & Gamble (UK),  EWCA Civ 407. The Court of Appeals relied upon a finding of the Tribunal:
 Here the potato flour content is over 40 per cent; it is the largest single ingredient by about 9 percentage points; and it is nearly three times larger than the other flours in the ingredients taken together. We have to give a yes or no answer to the question "are Regular Pringles [partly] made from the potato, from potato flour or from potato starch" and we are bound to say yes. There are other ingredients but it is made from potato flour in the sense that one cannot say that it is not made from potato flour, and the proportion of potato flour is significant being over 40 per cent. The fact that it is also made from other things does not affect this.
See id. at ¶ 33. Given this finding, the Court of Appeals stated that "[t]here is more than enough potato content for it to be a reasonable view that [a Pringle] is made from potato." See id. Thus, ending the question of whether Pringles are a food that is not subject to VAT or an excepted potato item subject to VAT.