ISDN pricing varies HUGELY by region and provider. When I first checked prices on it when I lived in Florida, with my usage levels, it would have been hundreds of dollars a month, because of per minute line charges. Then some years later, I was hearing of people with ISDN lines that cost only as much as a phone line. The costs depend on the distance the line has to run, and whether your phone provider charges per-minute for usage, and whether your ISP charges per-minute or flat-rate, and whether you can get an ISDN service ISP that isn't going to be a long distance call.
ISDN can be considered a digital phone line. The ISP has to have an ISDN adapter on their end, which many don't since it's a less than popular service residentially. When you dial up, the connection is established just like an analog modem (but within a second or two rather than the long handshake of analog). You can get one or two channel service at 64k per channel, or possibly even bond several lines together for higher bandwidth if the ISP supports it. Some ISPs do all the work for you, getting the line installed and having the telephone company bill everything to them so you only get one ISP service bill, while in other cases you'd have to get the ISDN line installed yourself, then sign up for service with the ISP just like for a dialup connection. An ISDN line can also be used to allow regular phone calls, if you have the right equipment. If you can only get service on a per-minute usage basis though, ISDN is not usually a good option. Even with a flat-rate service, it certainly doesn't compete with other types of connections.
Satellite is a good option if you can get it and are not dependent on low ping times. The latency of the signal to and from the satellite is very high, but you do get decent speeds these days. It is still relatively expensive though.
T1 service will never be a residential service. A T1 line requires special equipment and wiring, unlike ISDN or DSL or cable. They also use the expense of T1 lines to make a large profit, which they couldn't do with it as a residential service. For the higher prices, you get better reliability and contracted uptime and repair times.
If you just want a little more speed, you might see if a dialup ISP near you supports bonded analog service. This uses two analog modems on each end to get double the up and down bandwidth, though it's still not nearly as fast as two ISDN channels.
Splitting the cost with neighbors is probably also likely a bad idea. Assuming a 700 dollar per month T1 service, with leased equipment included in the price, they would still end up paying 350 a month for half the 1.5Mbps speed in each direction. A 768k DSL line is well under 100 dollars if you could get it, and most people will balk at paying that huge a markup.