As always, Jessie, it depends on what is of value to you. My DW and I don't get jazzed about eating out, so we don't spend $$$ at the fancier restaurants like some do (we WILL be at 'Ohana, though!). We won't be spending much on adult beverages or souvenirs. We do value
highly our nights in the MK - we have many fond memories both as children ourselves and as parents of DS, and hope to make more as we go just the two of us. The way the park lights up; the different look and sound of the attractions at night (even the tame Jungle Cruise takes on a more sinister feel in the dark); the growing feeling of being 'on your own' as the park empties at 9 PM, 10 PM, 11 PM; heck, the ever-shortening lines! And the Halloween theming will be an extra thrill.
Some foks will spend $200 at Victoria and Alberts, others will buy a couple of drinks at each and every country in WS - we'll take that money and have two nights until midnight at the MK!
And since you're going to WDW, you've already eliminated yourself as a 'cheapie charlie'

. Now you simply have to figure out what is going to add to your trip.
Lime green ribbons ready,
Erick