Drug addiction is a form of substance dependence, whereas toy addiction is a type of behavioural addiction. So it's probably more accurate to compare it with other forms of behavioural addictions like addictive gambling or video gaming etc. But fundamentally speaking, substance addictions and behavioural addictions are still all forms of addictions.
Symptoms of addictions include:
* Impaired control over the substance or behaviour. e.g. when HasTak releases another crappy repaint or a toy that seems overpriced for what it is, most of us would say to ourselves, "Screw that," whereas an addict would be like, "What a crap toy. I must have it!"
* Preoccupation with the substance/behaviour, so like you're constantly thinking about buying a new toy (as opposed to thinking about and enjoying the toys that you already have).
* Continued use/behaviour despite consequences - in this case, the guy doesn't even like his toys... doesn't play with them or display them. But he feels compelled to keep buying them.
* Short-term reward, long-term cost. e.g. if you're only buying Transformers to enjoy the experience of purchasing them, as opposed to buying Transformers and enjoying the toys for years to come. I still play with my G1 toys... just a few days ago I was making my G1 Rodimus Prime and Galvatron battle each other.
* Tolerance. This is when the body adapts to the substance or behaviour (thus it no longer gives you the same 'rush' or 'high'), and thus the user requires increasingly larger amounts to achieve the original effects. e.g. buying a new toy once a month no longer thrills you, so you buy a new toy once a fortnight. Then this becomes dull and you end up buying every new toy that you see on shelves as frequently as possible. When this no longer satiates you, you go online shopping for toys that aren't available in your region... and beyond that you start an eBay account and start splashing out for toys that are no longer available in your time! (i.e. vintage toys). I'm not saying that everyone who collects vintage toys off eBay is an addict, remember we're talking about people who enjoy the purchase more than actually owning these toys. So whereas someone might go, "Woot! I have a Grand Maximus! Can't wait to enjoy this toy!", the addict would be, "Woot! I have a Grand Maximus! Can't wait to put this toy in storage and hunt down Battle Gaia!"
* Withdrawal. "Aw man, there are no new toys out that I wanna buy. I'm not interested in Transformers no more." I can see how a lack of new toys is extremely frustrating, for sure... but as I've often said before, during periods of "toy droughts" (especially the late G1, G2 and late RiD years) I felt frustrated that there were no new toys too. But it never stopped me from enjoying the toys, reading the comics and watching the videos of Transformers that I already had. As most of you know, I've been an avid and dedicated fan and collector of Transformers non-stop since 1984... there have been times when my passion has slowed down (G2 years), but it's never stopped.
* Denial. I know a guy who's in complete denial that he has a video game addiction (and thus refuses to seek help). His marriage has broken down because he was neglecting his wife and children and household because he was just constantly gaming. He's just completely anti-social.