Have no idea how you got rid of them - (You didn't explain that.) - or what they were.

If the problem was fungus gnats, I wonder what was done "at great expense."

Please explain where the critters were;
What they were doing;
describe them (size, color, and more);
and what you did.

Fungus gnats, if that is what you had, can be a problem when potting soil is kept too wet, but they can be easily controlled simply by allowing that potting soil dry out between watering's. "Great expense" is not necessary to control these wee pests.
If you used pesticides in your house, and have children, this may be of some interest.
http://www.policymic.com/articles/61375/pesticides-are-lowering-your-iq-and-giving-you-neurological-disorders

Here is a link that might be useful: control of Fungus Gnats

This post was edited by kimmsr on Tue, Feb 18, 14 at 6:43

They may have been fungus gnats but they INFESTED the house...flying into my mouth and nose...unbelievable. The expense was the cases of ammonia I bought. Was told by an exterminator to pour straight into the rails of the windows to flush the BABIES out. I used jar lids filled with drops of Dawn and water...different times juice....vodka...EVERYTHING I read and was told would work...RIGHT..I changed the water in EACH lid in each window night and day...and YES, I would find gnats in the lids every day and night. Finally I think by killing the babies...they lay thousands of eggs....and having the lids to lure the adults...I FINALLY was able to see less and less. i am so worried to buy new soil but I love to grow anything in or out side. Very bad experience.
The gnats were small and would stay in the soil until I moved the pot then they were on their way around my house. I'm so afraid to plant anything again. Thanks for the responses.

I don't know what my ZONE number is. I live in Eugene OR

You need a firm ID before you can attempt any sortof management.

Take samples to the Lane County Extension Service.
This is their page with the contact info you need:
http://extension.oregonstate.edu/lane/

Then come back to let us know what you learn. What they are. And the recommended management.

Oh yes, we would sure like to see an image.

Here is a link that might be useful: Lane County Extension Service

This post was edited by jean001a on Wed, Feb 19, 14 at 1:36

Which Plant Hardiness Zone you are in is of little value since all it tells us is which plants will likely survive a normal winter in Eugene, OR. Eugene, OR is of much more value.
What that "exterminator" told you is of little use for Fungus Gnats or much of any other insect.

This post was edited by kimmsr on Thu, Feb 20, 14 at 7:29

Over watering and poor draining soil are usual causes. Allowing a longer wet/dry cycle will slow them down.

Top dressing soil with diatamaceous earth will help kill the adults as they emerge, using a light hand as it is a soil conditioner and overuse will raise pH. 1-2 tsp per gallon. A thick layer of perlite is also beneficial.

Mosquito Dunk, Mosquito Bits, etc (BTi, Bacillus Thurigiensis israelensis) can be top dressed or mixed into fresh bought soil, at a 1/2 tsp per gallon. A bacteria that will kill the pupae stage, preventing the next generation. Takes 3-4 weeks for full effect. Read product warnings thoroughly.

Neem oil and SM90 can be used as soil drenches, SM90 being a little pricey.

Yellow fly traps will catch fliers, and give a stationary bug to compare with the IPM link provided above. It is very important to catch and remove fliers, as they can lay an inordinate amount of eggs in a short time.