It's a bit tricky, and in my understanding the crux of the matter lies in how to see 'wealth'. Like many other pre-industrial societies, and also our own in some aspects, material possessions are not always freely tradeable on the market. As such, they do not have 'monetary value' in our sense of the word. The symbolic value of objects is also important, which means that a certain object loses lots of value when it is detached from its owner.

The essential theory behind this was laid out in Marcel Mauss' Essay sur the don, translated as 'the gift'. The idea of a separation between 'gifts' and 'commodities' has to do with whether an object can be separated from its owner, in other words, whether it is 'alienable'. If an object is inalienable, it can still be 'given' to another person, but the previous person still has significance in relation to the object, and hence also to the new owner. This concept of a gift society is particularly evident in the literature of the time, such as in Beowulf. Tolkien in fact made use of the concept in his characterisation of the One Ring in The Lord of the Rings: even though the Ring was in possession of someone else (Bilbo, Gollum, whatever), the Ring still held a 'reference' to the evil Sauron, its original owner. An object (in Tolkiens case the Ring) could thus 'influence' the owner, as if it is an extension of the person itself.

In western society we also have such notions of inalienability, such as with particular heirlooms. A wedding ring is a good example. What do you do with a wedding ring after death? Even though these are made of valuable materials and could be sold for money, people choose not to do so because they are a 'reference' to their owner. The ownership of the wedding ring does not end with the death of the owner.

In such a society, it would have been impossible to 'inherit' the symbols of personal authority, such as the scepter in the Sutton Hoo grave, because these objects refer to a person who is now dead. In their society, the objects in the Sutton Hoo grave are no longer 'valuable' because they could not be exchanged for things like food or money.

Another factor is of course the belief in an afterlife, which necessitates useful items for the dead person to use, such as food or tools or a house. We do not know whether the person in the Sutton Hoo grave was a christian or a pagan, and we certainly can not know the personal beliefs of the people who buried him.

Besides this there is also the factor of the inheritance of power. To construct an elaborate grave fashioned with loads of important artefacts shows that the people who buried him (including the new person in power) can miss this stuff, and thus are influential or important in their own right as well.

Thus there are (at least) three dimensions in which the Sutton Hoo grave can be explained: from a societal framework, incorporating widely held attitudes towards possession, from a personal framework, taking into account personal beliefs, and from a systemic framework, showing the material purpose of the practice. For further reading on attitudes towards wealth and material possessions I would recommend Appadurai's The Social Life of Things, for things specific to Dark Age germanic practices Bazelmans By Weapons made Worthy, and for different attitudes towards burial Parker Pearsons The Archaeology of Death and Burial.