I have used these w/great success.
https://www.amazon.com/gp/product/B000I6K3JY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
I guess success is relative. But I have never had a bug problem. Keep about 5 of these in a 5' X 6' grow area. They last like 2-3 years, always stay sticky. So, what I'm saying is I've never had an insect problem, yet my traps catch plenty of little critters. So any problems with insects are "nipped in the bud" maybe?
So in my opinion it's pretty cheap insurance. Would I have crashed and burned without them ? Probably not, but maybe. I never sensed an insect problem other than soil gnats, which is probably most of what I was / am catching.
Anyway, about 50 Cents apiece. Call it around 1/2 USD or Euro. I get probably 2-3 years from each, at which point they get Gnatted up".
So in retrospect these are dirt cheap, I have no idea if they are adding much to the party. But I have no bug problems and after a couple years they are pretty much get packed w/small gnat sized critters.
As it's never developed into a problem I have not paid much attention to things. Just keep them (bug strips) up and keep going forward. So ridiculously cheap.