I can see what your problem is. You want a serious qualification that is recognised by employers; at the same time you want to do it quickly and at a low cost. The two criteria you mention are hard to fulfil. Anyway, here are my ideas:
Think about what your ultimate goal is. It seems to me that you teach English to fund your studies in Philosophy. This is different to making TEFL into your career. Decide what you want to do in the future. It’s easy to get absorbed by your current situation and problems; but it’s wise to keep your ultimate goal in mind when making a decision.
I suggest you find out more about schools in your area. For example: how much do they pay their teachers? Is it possible to teach at the university on a part-time basis? What qualifications do schools in the area ask for (consider state schools and private schools)? In Italy, a degree and being native speaker might be enough to get you a job. When you have this information, you will be better placed for making a decision.
Have you considered charging more for your private lessons? You could also try teaching a group of students privately. You might be able to get a group of 3 – 4 adults or children who want to study together. This would increase your income. One advantage of teaching privately, is that you have more autonomy and more choice over which hours you teach.
Some schools have their own in-house teaching method. These schools often take teachers who are not CELTA qualified and provide training in their methods. Because these posts are at entry level, they pay less. The advantage is that you get training, get experience teaching in a school structure and can mention the work on your CV.
You could also find out if schools in your area hire teachers who have done a weekend course. These are short, as the name suggests and in the UK cost around 200 pounds which is approximately 300 euros. There are many of these courses available. Before starting one of these courses, check whether they will help you gain entry into the sort of school you want to work in.
Finally, for a discussion of on-line courses, you can look at the Teacher Training forum on Tefl.net, there are some posts about the topic in May 2006.