Ah, I feel you. Sorry, I somehow totally misread "financial commitment" from the conventional meaning because of Oxford's (delightfully?) stilted application language.
I was in the same boat while biting my nails waiting for news on the funding I was targeting. Even after pouring over the different options, I just couldn't get it to work out given their incredibly expensive international tuition rate. But man I was really prepared to be disappointed for exactly the same reason you're referencing. "How can you get into Oxford and then turn them down!" said a little voice in my head. The way I looked at it with all the numbers on the table, the amount in loans that I would have had to take out to make it work would have completely ruined any joy I got out of the experience in the first place. It could very well be a "good" investment in the raw financial sense. Your increased earnings over a lifetime might break just exactly even or put you ahead. But in reality, paying off that increased financial burden in the mean time will be a club over your head for years.
Of course maybe your financial situation is substantially different! Those were my thoughts on it, though.