Summer, especially for European travel, is all about the coach cabin. Planes fly full. But business travel dries up, which means paid business travel dries up. As coach tickets get more expensive, business class prices fall, the spread is much smaller than usual.

United is looking to goose some extra revenue from their business class cabin during the lull in premium traffic by offering a 20% discount on both the mileage cost and the cash co-pay for upgrades requested online by July 28 for travel between July 24 and August 12.

The discount applies to travel between the Continental U.S. plus Alaska as well as Canada and Europe, Japan, North Asia, Middle East, Central/Southern Africa or Southern South America. Interestingly the discount does not apply to South Asia.

Take a discounted coach fare to Europe — an upgrade normally runs 20,000 miles plus $550 cash each way. This offer makes it 16,000 miles and $440 each way per person.

Of course, that’s still 32,000 miles and $880 cash on top of the paid fare roundtrip.

This is for pretty close-in travel of course. When buying tickets far in advance, especially during summer or holiday periods, one can often get restricted business class tickets for the same or less money than buying coach and upgrading.

The cash co-pays are a killer, and the ability to upgrade discounted tickets generally only applies to the airline whose miles you’re using. Partner upgrades are usually going to entail buying full fare tickets.

Which is largely why upgrades don’t make much sense for most people, especially compared to the value offered award tickets — unless somebody (like your employer or another business) is buying you a full fare economy or a business class ticket, or unless you are looking to buy (expensive) elite qualifying miles towards status.

Last month I wrote a piece for Conde Nast on why upgrades are no longer a great value use of miles.

The advice used to be that international upgrades were the single best use of points. That’s no longer true — because of the introduction of cash co-pays making upgrades less valuable, and the development of airline alliances making award redemption more valuable.

Discounts are always appreciated, if you are requesting an international upgrade from United do it now to pay fewer miles and less cash. But don’t confuse that with the best use of miles, or even an exceptionally good deal.