click eventini inputa vermişsiniz hocam, butona vermeniz gerekmekte. Aşağıdaki şekilde çalışması gerekir.

<div class="form-group">
        <label for="OutSum">@lang('app.sum')</label>
        <input type="text" class="form-control" id="OutSum" name="summ" placeholder="@lang('app.sum')" required>
        <div class="col-sm-12 text-center inamountDiv">
            <button type="text" class="btn btn-primary price-btn" id="10" data-price="10">
                10.00
            </button>
            <button type="text" class="btn btn-primary btnIN price-btn" id="20" data-price="20">
                20.00
            </button>
            <button type="text" class="btn btn-primary btnIN price-btn" id="30" data-price="30">
                30.00
            </button><br><br>
            <button type="text" class="btn btn-primary  price-btn" id="50" data-price="50">
                50.00
            </button>
            <button type="text" class="btn btn-primary btnIN price-btn" id="100" data-price="100">
                100.00
            </button>
            <button type="text" class="btn btn-primary btnIN price-btn" id="200" data-price="200">
                200.00
            </button>
            <input type="hidden" name="type" value="add">
            <input type="hidden" id="AddId" name="user_id" value="@if(isset($user)){{ $user->id }}@endif">
            <input type="hidden" name="_token" value="{{ csrf_token() }}">
        </div>
    </div>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
    <script>
        $(document).ready(function () {
            $(".price-btn").on("click", function () {
                let price = $(this).data("price");
                $("#OutSum").val(price)
            })
        });
    </script>