When a women buys herself an outfit as a gift for her partner, that's usually because it's something he would enjoy seeing her wear (or take off) as such, he gets something out of it. A figure of your waifu is something you and you alone can enjoy, your waifu doesn't get anything out of it.
...unless you believe the figure serves as some sort of interdimensional conduite that opens a gateway across the planes of reality allowing you to better interact with your waifu in her own realm of existence... but even then that's not much of a gift to her unless you believe she's over there waiting for you. otherwise such a scenario would be comparable to a stalker molesting a voodoo doll of the person they like.
But that's just how I see it.