HarryW

You might choose to consider wealth to exist in the absolute sense but you can only get away with it when looking at a subset of the whole economy.
Someone plants a tree. It's a very fast growing tree so after a single year of growth, it is a proper full-size tree, ready to be cut down and made into lumber. The person who planted the tree sells it. They have increased their personal wealth through owning the land, planting the tree and waiting. Who has lost wealth through this person's gain?
The person in this example has increased his personal weath but, if you consider the whole economy, one more tree means that the demand has reduced by one. The supply has increased by one. The value of trees (in his economy) has declined (ever so slightly). Perhaps this guy was going to have to buy someone elses tree until he grew his own. That's one less customer for some one else, and unless someone else grows one less tree, the unit value of a tree will drop (OK, only by a small degree but we are only talking about one tree here).
You are a programmer, and you spend a year sitting at home furiously working on a new compression algorithm. After a year you have completed the algorithm to a saleable extent, and you patent it and license it for use by various companies. Your new compression techniques saves them money in the long run by reducing the need for storage space and reducing backup times. You accumulate wealth from your effort, and so do your customers. Where has the wealth come from?
OK, this time, we've affected the economy on a much larger scale. The demand for disks (and other storage devices) will drop considerably. The unit price of disks will drop unless the production is greatly reduced and then lots of people will lose their jobs.

If wealth wasn't relative, there would be no such thing as inflation. It all comes down to supply and demand. You define something's worth in terms of how many people want it (and consequantly how much they are willing to pay for it). If everyone has too much of something, it is worth less because people aren't willing to pay much for it.

In absolute terms, how much is a lump of gold worth? How much is a sack of grain worth? A sack of grain is worth a lot to someone starving in a famine but not much to someone who already has more food than they can eat. How can anything have any worth in an absolute sense?