Hi Sigrid,
I know how you feel. Some of my book signings at mall bookstores were great. Other times I was mistaken for a store employee and asked for directions to the bestseller shelves or the restrooms. I drove home thinking I was building a LOT of character.

Have you considered:
a. Charging for your appearance at the library, hospital or nursing home? These venues do have a budget for programs. I only sold three books at a library, but the $50 I was paid to come speak for one hour lessened the sting.

b. Marketing costs money. I don't know any way around that. My publisher has spent a lot of money on marketing. But I feel I must do my part to get the word out too. We all spend on clothes, gas, time, buying our own books, etc. to help promote it. But if we did nothing, we wouldn't be promoting.

c. Keep looking for new markets. I sold more books at a grocery store than I did at bookstores because the women I was trying to reach were there in numbers!

Hope this helps.