So here goes:
Salary is low but depending on the industry it can be higher than many full time jobs. People in banks can get up to 4.5k/5k a month gross.
The salary is low, because your responsibilities in an internship (usually) are low, so not much is expected from you.
All the usual deductions are in, but be happy for it. You have full accident insurance, and if you work for a year you qualify for unemployment benefits if you can't find something and have a valid permit. Also payments to your pension (that you can transfer later or get in cash for certain conditions).
Last but not least the next calendar year after your first salary you might be eligible for a financial support for your helath insurance payments, depending on level of salary and how much you worked. You will also receive a lump sum for retroactive support of the past year, so all you have to do is hold out for a while.
All in all internships here are very good and much better than most places, especially due to the salary. I've been living for a while with 3 and change per month and its manageable for a young student looking to start.
You connect, network, and if you play your cards right and the circumstances allow it, you can even get a job offer after it. Most people I know were lucky and got meaningful internships with project work etc, but some did get the shaft and ended up doing menial BS day-in, day-out. In any case, on the 25th of the month you'll be happy you're doing it in CH and not somewhere where it might even go unpaid... My brother is about to start an internship for about 120EUR/month in Greece.