I don't know a lot (anything) about Burberry, but would it be possible to buy a more classic Burberry trench on consignment or something? Maybe you could find one at a more reasonable price.
I will say again I have no experience with Burberry in particular. My husband and I both have decent jobs, but I could never justify that kind of expense on a coat! However, I do shop at stores ranging from Target to Rave to Forever 21 to H&M to Banana Republic (I rarely go to stores more expensive than BR). I have bought things at Target that have lasted held up for years, and have a shirt I bought at Rave (similar store to Forever 21) that I've had since 2005. It's not really my style anymore, but I wore it all the time for several years and it's still in great condition. In contrast, I got a pair of jeans at BR that cost $80 (well, I waited for a sale), and they shrunk ridiculously! What I'm trying to say is that lower cost items can sometimes be good quality, and higher cost is not always better.
Also keep in mind that you're purchasing a light-colored garment, meant to be used as outerwear in wet weather. Even if it's the highest quality, how likely is it that it will remain un-stained and un-damaged for many years? Alternatively, will you end up being afraid to wear it because it cost so much, and have to wear a cheaper coat for "everyday"?
Ultimately, it's up to you. If you have the money to burn, why not? But I don't think it's a wise purchase if you worry AT ALL about your budget!
ETA: is there a particular reason you NEED a high quality trench? I mean, people NEED good interview suits and things like that, but is there an element in your lifestyle for which you would need this kind of thing?