From experience, the premium is between a few euros and around ten euros per month, depending on the insurer, age and scope of the option. Measured against the risk it covers, that is little.
A single diagnosis in the meantime, for example psychotherapy that has started or newly treated high blood pressure, can mean a permanent risk surcharge of 25 to 30 percent in a regular application or prevent acceptance altogether. The option is therefore insurance of your own insurability. For tax purposes, the premium counts as one of the other provision expenses, whose maximum amount is usually already used up by the basic cover, so do not plan on any deduction effect.