No. Wishpicks doesn't have a way to split the cost of one gift between several people. There's no group gifting, chip-in, or money-pooling feature, and it never handles gift money at all.
A reservation is a plain "one person, one item" marker. There's no amount attached to it, so there's nothing to divide.
What you can do instead
Have one person reserve and buy the gift. Reserving marks the item as taken so no one else buys it too. See "Do I have to reserve a gift before I buy it?" Then settle the money among yourselves, off Wishpicks: agree who pays the store and how everyone pays them back.
Good to know
"Contributor" is about editing, not money. On a shared wishlist, a Contributor is someone who can add and edit wishes. It's a co-editing role. See the Shared Wishlists & Collaboration collection.
You buy at the store, not on Wishpicks, so there's no payment here to split in the first place. See "Does Wishpicks process payments?" and "Can I buy a gift directly on Wishpicks?"
Reserving costs nothing. It doesn't charge anyone or place an order; it only marks the item as taken.