Last weekend, Apple doubled the price of upgrading the MacBook Pro 13in's RAM from 8GB to 16GB. The increase occurred all over the world, including the UK, US, Germany and Sweden, which ruled out any explanation based on tax or currency exchange rates.

Apple has now gone on record to explain the increase and take responsibility for it. In a highly unusual step for the company, a spokesperson told The Verge that the increase is a correction from a price that had previously been too low.

It should never have cost £100/$100, in other words. After all, the same upgrade costs £200/$200 on all other Macs that come with 8GB by default, including the MacBook Air and iMac.

However, that explanation still doesn't quite wash, as The Verge points out. Because this is different RAM we're talking about: the cheapest MacBook Pro (which you shouldn't buy) uses the older LPDDR3 type of memory. Other Macs, including the MacBook Air, use LPDDR4X, and it actually made sense for upgrading this newer form of RAM to cost more money.

This article originally appeared on MacWorld Sweden. Translation by David Price.