Those look equivalent; one is defined in terms of intention, and the other in terms of mechanism.
Pretty much. Except that the type of discrimination I've been discussing is capturing low end surplus, by making use of a seller's excess supply that would go to waste unsold at a higher price. For example, if a factory can produce X many widgets a month, but the market will only support Y widget sales at their full price, then they can sell X-Y widgets at any price higher than the truly variable costs (i.e., consumables only) and receive the difference as pure profit. This is extremely lucrative for the company, and benefits consumers who would or could not have bought the widgets at the higher price. But it only works if the company can prevent its full-price buyers from getting them at the lower price.
And every real-world example of price discrimination I know of works like this. Coupons, loss-leaders, rebates, special fares, sales, closeouts, last-minute vs. advance prices, factory outlets/seconds... heck, I just saw a real estate agent's ad offering to sell your house at no commission... if you use him to buy your next house. Granted, that's not exactly a tiny market segment, and is probably a bit more like a specialization than it is true price discrimination.
Anyway, the idea that a business raises prices to squeeze more money out of a select group is mostly silly; only a poorly managed business would establish its going rate any lower than what the top end of the market can bear in the first place! Ergo, any other prices offered for the "same" widgets are going to be lower, and any new higher prices will be justified by added value in the new offering, or else the market won't pay the higher price.
(Absent monopoly power, of course. Comcast keeps raising the rental rate for its modems, for example, without providing any new benefits. And that is price gouging, not price discrimination. In a market with real competition, you can't price discriminate by raising prices for a select group without some sort of justification, if you want to keep making sales to that group.)
And every real-world example of price discrimination I know of works like this.
That might be availability bias, though. If you deliberately try to not waste money, you're probably avoiding many of the ways that you can price discriminate up. Software as a service has many examples of price discrimination the other direction; here's Patrick MacKenzie on the subject. (It's a recurring subject, there might be a better place to jump in, but that'll get the idea across.) Many people in companies are willing to pay 10X in order to say they're getting the Ente...
I was going to wait to post this for reasons, but realized that was pretty dumb when the difference of a few weeks could literally save people hundreds, if not thousands of collective dollars.
If you fly regularly (or at all), you may already know about this method of saving money. The method is quite simple: instead of buying a round-trip ticket from the airline or reseller, you hunt down much cheaper one-way flights with layovers at your destination and/or your point of origin. Skiplagged is a service that will do this automatically for you, and has been in the news recently because the creator was sued by United Airlines and Orbitz. While Skiplagged will allow you to click-through to purchase the one-way ticket to your destination, they have broken or disabled the functionality of the redirect to the one-way ticket back (possibly in order to raise more funds for their legal defense). However, finding the return flight manually is fairly easy as the provide all the information to filter for it on other websites (time, airline, etc). I personally have benefited from this - I am flying to Texas from Southern California soon, and instead of a round-trip ticket which would cost me about $450, I spent ~$180 on two one-way tickets (with the return flight being the "layover" at my point-of-origin). These are, perhaps, larger than usual savings; I think 20-25% is more common, but even then it's a fairly significant amount of money.
Relevant warnings by gwillen:
Additionally, you should do all of your airline/hotel/etc shopping using whatever private browsing mode your web browser has. This will often let you purchase the exact same product for a cheaper price.
That is all.