An my friend, bupe is a maintenance medication, and very long acting. I was on it for ten years, from the first time it came out around here until about 6 months ago. The DEA visited the clinic I was going to for overuse of Subutex as opposed to Suboxone, so they had to switch everyone to Suboxone. Fortunately I let them know that the nalaxone gives me migraines and I became one of three people on plain ole bupe. My best advice is to beg your doctor for subutex because they come in generic for $3 a pill. I know that's still not cheap, but I would also recommend you get more than you actually use, so you can stockpile. I was on 2 8mg a day but only took a half or whole one. This will give you plenty of room if you can't afford to go .
Also something I have done is split the cost of the clinic/meds with someone else who also needs bupe maintenance. This way you pay half the cost for half the meds, and since bupe is reletively safe, in my mind seeing a doctor isn't necessary.
Also, I shot up bupe for YEARS, mostly twice a day. I was able to maintain on 2mg a day, much less than sublingual. Word of advice: DON'T do that. I now have severe heart problems and bupe is the only thing I've shot up regularly like that and I don't like stims. Doctors will tell you you can't shoot it up but you can shoot up both bupe and bupe/nalaxone and get high, especially if you're not using other opiates.
What do DR's know anyway, they were prescribing me 8mg Xanax, 16mg Bupe, and 60mg Adderall for conditions that I had never been diagnosed with before. They are definitely in it for the money, as long as they get their cash they'll write you anything if you do the little dance of knowing the symptoms of those disorders.