Strange. Why has my mortgage gone up $100 in the last 7 years then?
Ok, well for shits and giggles, that $250 every month for the next 30 years, compounded monthly and adjusted for inflation, would turn into $765,260.51 in 30 years (which would be $365.5 k at present value). That's assuming the market grows at it's historical average over the last 100 years. You would put 90k into that and get what amounts to the current buying power of $365.5k. Since rents are typically related to mortgages, you could feasibly ramp that $250 up over time...but for sake of simplicity we'll keep it round.
Conversely 225k house at $1250 per month would have cost you 450k (actually, a lot more than that if you account for increases in property taxes, upkeep (roof, sprinklers, water heaters, etc etc)...most of which you aren't exposed to as a renter. At the end, you're basically at a zero sum there since the future value is roughly 450k (which equates to about 245k at present value).
So you could take your 765k, buy your now 450k house, and pocket $315k.
You're right though, with current rates as they are, the difference between a mortgage and rent on a comparable property isn't much, and in that situation the equation becomes essentially equal. Also, offsetting rental income does come into play, and if you can pull that off with a livable situation (i.e. essentially transparent renters, or renters you don't mind having close by), then you're ahead of the game. Trust me though, being a landlord isn't that awesome, and (this probably goes without saying), but don't "count" on that income to be able to cover your mortgage.
I get wanting a home and wanting your own space, and I have no problem with that as long as people are conscious of what that means for their financial goals. In my eyes a home is merely a reasonably stable savings account, and that may very well be what you are looking for financially. Some people's financial goals don't fit with that, and they may want to look at what the opportunity cost of that mortgage is when compared to other readily available investments.
Cody