Jumping into the fray after trying to read most of the posts. A few of my own personal experiences/observations from someone who started with nothing, but have had a successful career (3 - 4 yrs from FIRE).
- Agree that there is some relative income where after your needs are met, additional income only buys so much more happiness. However, creep sets in and I find your "needs income" natural rises as income does. As someone who is a sole income provider and self-employed, I find that as of every Jan 1 when my income is 0, I operate with extreme motivation (some healthy fear as well) to hit my nut (needs/budget expenses) asap. Once I hit that number, I find I am still motivated, but I tend to downshift my drive.
- Regarding nice cars... Yeah, I made a conscious decision to buy a 2015 BMW 650 which I love driving and get a "happiness" return on, but that's just me. In my case, I acknowledged all the reasons I shouldn't buy it, but frankly, with my income/savings/living significantly below my means, relatively speaking for me, it does not jeopardize my RE. My strategy is to hold it for 3 yrs, enjoy it, then go back to a "practical" car.
- My wife and I took 2 of our college age kids to Italy recently. While we could have back packed, taken the train everywhere, stayed in hostels, we had the means to stay in nicer hotels, rent nice hotels/B&B, take a personal wine tour with driver/guide, etc. would we have had a good experience back packing... probably, but I can tell you in our case, spending the extra $ improved the experience for me/us.
These are just a few of my own experiences. My plans are to spend less than I do now and simplify once I FIRE, but my RE income goals are still very high compared to many on this site. Having started with nothing, I think I could significantly ratchet back my "needs income", but I would be lying if I didn't get some better experiences/some additional happiness by spending more in certain instances.
Ok, now you can hit me with a MMM face punch!