A film like Slacker or Stranger Than Paradise would be far more affordable to make now; on digital video - but, the likelihood of such unique/interesting off-Hollywood movies being made in great numbers is still slim, and the chances of such indie work getting wide distribution is still small.
It is however far more easier now than in the early Jarmusch (late 70's) & even early Linklater (late 80's) days to get started with filmmaking due to digital video and the availability of filmmaking information on the web.
So, what, if anything, guarantees success in the indie world? And is it easier to achieve now than, let's say, 20 years ago? Well, it depends on how you define success. It is far more easier to make a feature length film - using digital video (can be done for around or under $2K - Texas Snow is a recent example) - and tell some people about it (web; sites, blogs, e-mail), and make it available to view & purchase on DVD (1000 DVDs can be made for around $1300 - $1500 from Disc Makers & other companies). Those factors, along with the availability of hundreds of new festivals - showcases - makes the current time period a better one in which to get an indie feature filmmaking career or habit started. Success could be defined as making an interesting movie and making it available for audiences. That kind of success is easier to achieve now than in the 80's (because it won't cost as much & the information on how to make it happen are easier to come by). Now, the Hollywood kind of success; making lots of money from a movie - that's always been difficult with indie films and at this point in time it may be more difficult to do with a good or great first time or second time feature than it was back in the 80's - due to several factors including competition for leisure time from many entertainment options that did not exist in the 80's.
There is one thing that has not changed; a quality crucial to getting indie movies made: dedication & perseverance. Ultimately, back in the day (Micheaux, Cassavetes, Sayles, Waters, Jarmusch, Lee, Araki, etc.) and now - the kind of people who will achieve any kind of success in the indie film world will be the ones who are 110% dedicated to the art/entertainment form and stick with it, continue to develop, and continue to go after the goal of making indie movies & actually succeed in making a movie ever so often. Such people, in the worst case scenario, will at least leave behind a body of work - several films. That, simple existence of movies created by someone, may be the most significant marker of success; ideas & viewpoints will be shared with new people (people new to indie film, or just younger people who were not alive or interested when the movies got made) and perhaps these new people will get something positive out of the movies; maybe an entertaining moment, maybe a shock to the system that totally re-writes their world view (hopefully for the better). Since there will always be a movie that makes more money & directors who become more famous than the ones who are famous now, and since all of this will end - ultimately - the wise thing (probably) to do is to really take a hard look at the challenges and see if making indie films is the thing that you absolutely want to pursue above all else in your life, in the relatively small (even if you live a healthy 70-80 years or so) amount of time that you have on this planet. If it isn't, go figure out what else you'd like to do with your time & go get it done. If, however, making indie films is the thing that is more attractive to you than anything else you could do in life, then dig in. Even with the availability of low budget production & distribution options, such a deep commitment is necessary, I believe, to get any kind of an indie movie made let alone a good or great one.
So, the good news, at least for some people who are worried about there being too many movies or too many good movies - making indie movies & getting them distributed has always been hard, and probably will always be so; meaning, only the deeply committed people - such people are usually few in number in most areas of life - will achieve a significant amount of success in the endeavor. Paper is cheap, but the world is not overrun with great literary masterpieces or even a ton of entertaining/creative books. There is a lot more of the human experience left to reflect and explore in books. Digital video & computer based editing & web publicity is cheap, but we are not being overrun with awesome indie movies. I think for the committed artist/filmmaker there will always be room for creating good or great works. And creating such works is most likely an option only for the committed filmmakers because film is not an easy art to master; it takes a while.
Being an indie filmmaker, or being an artist of any kind, is its own greatest reward. For most people no amount of money is enough and no amount of fame is enough. But, if you think you'll get your happiness primarily from being able to create & share movies - then being an indie filmmaker may lead to a rewarding existence for you. Everything, however, has a price. First & forever it takes a deep commitment to be an indie filmmaker. After that you need tools; luckily for you the tools you need to make movies are now much more readily available than at any point in the entire history of the medium. So now is a great time to be alive & active as an indie filmmaker. Jump in now if you've always wanted to do it, and if you are doing it, get deeper into it; for, I think, that - commitment/perseverance/getting it done regardless of the obstacles - is the path to all manner of success in indie film.