The shop i used to work in had those EVERYWHERE, we must have killed 10 a day every day, for 2 years and they never seemed to die off. I was the only one who ever got bit though, and it was a dry bite so nothing happened. Sticky traps are the only thing that seemed to work, we had three exterminators come out and spray but it never seemed to work, the last one to come out told us they aren't as susceptible to pesticides as other pests.
spraying for spiders doesn't work as well because they have long legs and can walk right through the pesticide and not be bothered by it. The only thing that really works is spraying it right on the spider.
I have to explain this to tenants all the time when they want us to send someone out to spray for black widows (which is what we have more of here). Two issues: 1) they don't come out in the daytime when pest control companies spray and 2) you have to hit them directly with the spray for them to be killed, please reference #1.
Tenants hate it when I tell the to get spray at Home Depot then go outside right when the sun is setting and spray all the ones they see. But it works. That's what I do here. I'm scared to death to do it, but I'm more scared of them breeding more spiders so I force myself.
Our pest control company will go out and spray, but tell us "absolutely zero guarantee this is effective..." (They do spray wood piles, though, and say that is effective as it will drip down into the wood and kill the millions of them that love to live in wood piles.)