The bouncer seat was my very first purchase at my very first mom 2 mom sale.
We used the seat all the time when he was an infant. It was nice if we needed to shower or something, he could sit up in the bathroom and be happy. Ours also had a vibrate feature which was nice when he was stuffed up and we were trying to get him to nap. We would also use it in the bathroom when he was congested. We would run hot water (or just take a shower) to get steam in the room. Another benefit was that it was pretty easy to put in the car and go.
Ours is not the same as the one pictured, but it is similar in its build and features. I paid $10 for mine, but have seen them cheaper quite a bit. I would still say that average is right around $10. I have seen nice, yet basic ones for $5, if you see one at that price, I would snag it. I have seen them as low as $2, but they are much older models.
Do you have a bouncer? How much did you use it? Did you get a good deal?