Now do some simple math.
Typical monthly expenses that are absolutely irrelevant to survival for Americans:
cell phone $100, tv/cable/movies/netflix/etc, $50+, internet $20+, gas $200+, car insurance $100+
Sacrifice just one month without wasting spending on all of those things listed for which you have nothing to show afterward and you can buy yourself a nice Busse that will outlast you. Priorities. 
Giving up paying for gas, car insurance, internet, or phone service is not always an option. Many people need to drive to work (to far to bike/walk, no bus route, or prohibitive cost of public transportation vs. own vehicle), need their car for safety/medical reasons, telecommute via the internet, need the internet to search for jobs because there's isn't stable enough or need the communication provided by it, or need their phone for work.
I'm currently without a car and bike 20 minutes to work in the 110 degree heat here in tucson because I need the money to pay off debt, and I couldn't reasonably spend 2,000$ to fix my car. I can't, however, safely give up my phone because it's necessary for when work calls me to change my schedule or request that I come in. I could give up internet, but it's my major communication between friends and family - if I give it up I have to rely more heavily on my phone which will increase costs (I'm on a gophone plan that varies between 10$-40$ a month, vs. the 60$ minimum cost for a monthly service).
Even if you give up all of those, the assumption that you will be able to afford a knife has to include the prerequisite that the person is making enough to afford those to begin with (full time job, or a part time job that pays exceptionally well), or that they can avoid immediately shifting that money towards other priorities or past debt payments.
If I get rid of every single extra expense in my life, I still can't realistically afford Busse Combat because I have 16,000$ in tax debt, and 4,000$ in credit card debt, all of which ends up at around 25% apr. Some of that was my own doing, some of it was because living expensive and high rent ate up credit when I was only able to find part time work (I've always held a job, just not always good ones). Any extra money I can shave off of comforts, nutrition, or necessity should immediately go towards debt, because it is both a current and future expense that limits my options.
My situation is common. Busse Combat is still an expensive company for me even if I adjust my financial priorities, do without, or go into even further debt to get them.
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