I started training the week before 9/11, talk about bad timing, but I stuck it out knowing that while I was in school and instructing the industry would turn around and it did. There will always be ups and downs in the industry.

The important thing is to do what you enjoy, and it won't seem like work at all.
Does it cost a lot to get started? Absolutely and yes you will not make a lot as an instructor but you certainly won't make as little as $25k a year for the first 10yrs.
I'm in my 8th year since getting all my ratings and I was making about 20k as an instructor for the first year and my first real flying job 135 was 40k.
Most of the guys I went to school with went to the regionals and are making 40- 60k.

Not trying to step on toes, just want to show another example.

I would say it has definitely been worth it and it's only getting better.