I just got an offer for "upgrading" to the new 4th edition PHP book for 50% of the regular price, since I bought 3rd edition some time ago. The offer was however for the hardcopy only, and I only buy PDF books, basically because I find them much easier to work with.

There's no discount on these upgrade offers when buying PDF books alone, you have to pay full price here, i.e. $29.95, while you get the hardcopy for only $19.95 with the 50% discount, which I think is a bit unfair, not least because it cost a lot more to produce a hardcopy than a PDF copy.

So how about at least lowering the price for a PDF copy to the same as the price for a hardcopy, in offers like these?

There's also another reason for some to buy PDF copies, whether they prefer them to hardcopies or not. Here in my country (Denmark) all stuff sent from outside EU goes through customs. This means 25% tax on top of the price; this isn't the real problem though, the real problem is that the postoffice charges $30 (yes, thirty US dollars) just to take care of the custom papers administration (you can do it yourself but it's extremely troublesome the way the system works, so no one ever does it).

This means that an offer like this for which Sitepoint charges $29.90 including postage (a really great offer if you're into hardcopies) will end up costing nearly $70 all in all, for people here in Denmark. It's much the same in other countries in EU, according to people I've talked to from these countries.