We spend (what I find to be) hideous amounts of money on our house, but it is mostly DIY upgrades. DH loves to tinker and have projects, and is way more ok spending money than I am, so in the 4.5 years we've lived here, we have:
Puprchased a new washer, dryer, and fridge when we moved in
Built a chicken coop
Installed a raised base and tile under our washer/dryer, and a laminate countertop over them
Painted a lot of rooms
Installed new light fixtures in 3 rooms
Installed a (gifted) Nest thermostat (which required re-wiring the connections, because the previous owner jerry-rigged, like, EVERYTHING)
Replaced the plumbing under our kitchen sink when it overflowed
Replaced the plumbing to our garage sink when it overflowed
Replaced 3 of our toilets with low-flow toilets (we did get a nice rebate for this one)
Epoxied our garage floor
Built shelves in our garage
Tore out those shelves and built hanging shelves in our garage
Blew insulation into our attic
Replaced a too-deep pantry cabinet with drawers instead
Built two separate iterations of raised garden beds
Installed a drip system for our garden
Ripped up our backyard and installed sod, paving stones, border stones, and gravel
Installed a sprinkler system in said backyard while it was deconstructed
Built a railing and bench on our deck
Built a little greenhouse for DH's bonsai trees and our garden seedlings
Replaced our roof and gutters (still paying that one off on a 0% interest cc)
Ripped up our bedroom - This one is still in progress. We started off saying "let's take down this ugly wallpaper and paint", and it turned into tearing out and replacing the floor, tile, the cast iron tub, sinks, counter, carpet, and wall color. And upgrading to a King bed.
Purchased a multitude of tools - lawn mower, weed whacker, paint brushes and rollers and drop cloths and pans, air compressor, nail gun, brad gun, staple gun, paint sprayer, miter saw, scroll saw, literally a metric ton of nails and screws
We throw a LOT of extra money at our house maintenance and improvement savings every month. I do love that DH can do all of these projects, and I do generally appreciate the end result, but man, it makes me cringe when I think of the total cost. I find sales and coupons and rebates wherever I can, but if you're going to do it, you may as well not cut corners and get a crappy end product.
We haven't had to replace any big appliances yet (AC, furnace, water heater), but I'm guessing they're reaching the end of their expected lifespan. Most of the money we've spent has been on completely "unnecessary" upgrades. The only necessary money we've spent was on the roof/gutters, plumbing replacement for sinks, and on getting a pipe replaced when it froze and exploded in our foundation after an unexpected early freeze.