Price creep can definitely be an issue. I think being well informed and having a firm idea of your requirements/wants helps quite a bit, and to get a good idea about that the best thing is to just get a cheap bike and ride it on your route for a while. After you have more time on your commute, you will know what you want in a commuting bike more precisely.
My current commuter bike is an old Nishiki road bike, complete with old down tube friction shifters and cheap, flexy caliper brakes. I use it to do 15km rides around the city, the occasional 38km ride to work, and am hoping to do a couple longer overnight trips before the summer is over. Is it perfect? No, but after riding it for a while I have a better idea of what I would want to change. One requirement for me, for example, is lower gearing than I currently have. The small ring in the front is a 42 tooth and the largest cog is 30 tooth, which is a bit high for steep hills. Now I'm trying to decide if I want to buy a triple road crankset, a compact double road crankset, or just put a triple mountain bike crankset on it.
My dad keeps telling me I should quit being cheap and just buy a nice shiny new road bike because they're "better" but when I press him about what is so much better about them he has few answers. Granted, they are lighter, but for commuting one will find that once you load it up with some water, spare clothes, rain jacket, maybe a couple tools, the weight of the bike makes a small difference.