I can relate to some extent. We also have a home that is well within our price range (we're still saving ~60%) but that is larger and more expensive than we really needed. Now that we're focused on fire, we are aware that the house is holding us back:
1. It will simply take longer to pay off. We could easily have found a great house for a lot cheaper.
2. More importantly, if we stay in this house longterm, our stash will have to be significantly larger to pay the higher taxes and insurance on the more-expensive house FOREVER. It is not insignificant.
3. Lifestyle inflation. We really do use the whole house, and we definitely enjoy the luxury. If we downsize, we'll miss it. (however, we know we can happily live in a much smaller house, so I'm not really that concerned...)
4. Friends and neighborhood- we have made awesome friends here and absolutely love the neighborhood: we don't want to leave it. Also, now that the kids have started school, it'll be harder and harder to uproot them and move.
5. While we are frugal with our utilities, there's no doubt cooling the larger house in the summer uses more electricity.
On the other hand,
6. One of our requirements for a house was a large yard, but since gardening is my hobby and I love it, we don't pay more for lawn maintenance. We do it ourselves.
7. We have been very careful to not acquire extra stuff to fill up the house. We are also careful not to try to keep up with the neighbors- we clearly live a less extravagant life in little ways (not eating out, paying for activities, impulse buys like DVDs every weekend or whatever. We're building our own patio furniture instead of buying a fancy set. Etc etc etc.)
8. My job is in the suburb where we live- I have a 5 mile commute on back roads.
9. When we bought the house, it sold in a week. It is in a very desirable spot, and we expect it to appreciate well and sell quickly if we decide to sell.
We're also in one of the best school districts in the state. This will actually make it MORE DIFFICULT for the kids to get into the top two state schools- the top 10% or so of each high school is automatically admitted...getting into the top 10% is not going to be a trivial task in this district.
On the other hand, the elementary school the kids are in is really fantastic. We love it. We love our neighbors. We love our neighborhood.
So- we will stay here another couple of years for sure. Our FI date depends on whether we stay in the house- 5-8 years from now, realistically (could be as soon as next year for SUPER BARE BONES FI, 5 years for downsizing FI, 8 years for current house FI.) So- it'll probably be an extra 3 years or so to stay in this house forever, given that we're already living in it. We'll assess in a few years if it's worth it to stay.
When we bought- the idea of ER hadn't crossed our minds, so the choice was quite logical. For crying out loud we were saving 50% anyway, pre-MMM. But now that ER is our goal, if we were buying again, we'd have found another house in the same area for less money. There's one in particular we almost bought that was smaller and less expensive but that would have served us well. We'd be much closer to FI, having saved more over the last 3 years and needing to save less TOTAL.
Anyway, I'm not sure what you're after here. Yes, your choice will delay FI. No, your choice is not mustachian. If I were in your shoes, I would not purchase a $545K home. I'd find a gorgeous home for $350 (or heck even $450) and save like crazy so you can CHOOSE whether to take time off with the kids or not. Think of the luxury of having zero concerns or worries about money at all. Zero second guesses about your choices. Zero sense of unease about the size/extravagance/energy consumption of your house. It's hard to put a price tag on that.