It is not impossible as many of us have done it. If the prices were lower then everyone would be free and everyone would get bored and end up leaving. It's meant to be hard for a reason. Now get back to the mines inmate!
Mine? Like 100k. I didn't get God till I was halfway through A rank. You can do it, takes dedication and patience.
How to get money on prison quickly: 1. Ask if anyone wants to trade money to prison in exchange for money on say, survival. 2. VOTE! 5k a day is pretty nice. 3. Once you get to B prisoner, mine that netherrack. You will be rolling in the dough. The prices might need to buffed a little, but honestly they are okay as is.
Personally I don't support this right now. Prices are ok as it is, and, as Sco said, if they were changed dramatically everyone would become free too easily.
It is not impossible. I'm [Free] myself and just be patient. Here are some simple tips to rank up: When you get to the B mines, mine the Netherracks. It's the most efficient mine and you'll get money quick! Just throw out the Glowstone, but save the Soulsand and Quartz. When you get to the A mines, just go back to the B mine and mine Netherracks. Unless if you have a super fast Diamond Pickaxe for Obsidian. You get $5,000 when you vote! That's a lot to me. I've seen other servers with the same price, but I can't advertise it.
Prison prices are good as is, we already have people who can live with the prices they have, why can't you?