Customers are proud of what they build themselves. This goes for essentials such as a flat-packed bed or bookcase and is also true for non-essentials such as plastic model kits.
Having to put some effort to get a finished item adds to the perceived value for the person who built it.
You can benefit from this bias by offering items which have to be put together by the customer. Everytime they look at or use the item, they will value it more than if they had not build it themselves.