Therapy helps but will not work in 100% of cases. I know of some people who quit cold turkey without therapy but the way was not cheap either. After a gambling binge that ruined his finances leaving him in debt there came a time when he hit rock bottom and as far as I know he has never gambled again. Normally to make it on your own you have to have hit rock bottom. And to get out of them if you have had serious problems you have to be clear that you can never bet again, not even a single bet.
Moreover addiction can be cured without it but if gambler has the will and determination to recover because without determination and will everything will be in vain just like wish that is too dreamed of.
However everything will cost money because when an addict is determined to stop gambling he will choose or do other activities to be able to slowly forget about it and of course each of these activities costs money because some gamblers escape by having fun or traveling with their family to get started approach to stopping gambling activities.
It just that personally it would be better for me to spend the money as treatment costs for gambling addiction rather than having to experience failure or bankruptcy before I can come to my senses and decide to want to recover.