Because my perception has been that the price tag on an Iron Man has more to do with the character’s popularity than how much it costs to produce one.
I don't know Hot Toys pricing strategy, obviously, but I don't think this is a huge factor--at least not the way that you mean it.
When the Mandarin was released, he was priced at $220. Other, drastically more popular figures that year were priced in the same range, so long as they were comparable (i.e. number of accessories, etc). Similarly, the MSRP for a Marvel Legends Hydra goon is the same as a Marvel Legends Tony Stark.
Think about it: wouldn't you be angry if HT produced a Sean Connery James Bond figure at $300 and a less popular Bond at $220, both with the same accessories? It wouldn't be a good pricing strategy because the optics would be terrible.
Instead, HT might produce the less popular figure with fewer accessories or features. That means it costs them less to produce, so they can charge the lower $220 price. For the more popular figure, they add more accessories and features, which allows them to charge a higher price that collectors feel is justified by the better accessories. They probably have slightly better margins on the higher priced figure because they charge more for, say, an extra head than it costs them to include it.
An Iron Man figure requires more pre production and engineering, and a drastically higher number of pieces be manufactured. We can assume they have a much more complex assembly procedure than putting pants on a stock body. Unlike most figures, they are fully painted from head to toe. All of these things increase the cost beyond that of a standard true type figure.
It wouldn't be practical to sink all that money into developing, say, the Mandarin, because customers would never pay the associated price. It IS practical to sink all that money into Iron Man because collectors are more willing to pay for it. They do, also, occasionally produce a handful of lower cost plastic Iron Men with fewer accessories and a simpler paint job to accomodate collectors at a lower price point.
So, to put it simply: they probably don't significantly increase the price of a figure just because it's a popular character, but they definitely include more expensive features and add ons for such a figure, which allows them to charge a premium price.
Ultimately, the rising prices suck, but HT is a business and these are luxury items so it's hard for me to get too mad about it. If they start charging more than what I'm willing to pay, yeah, I'll stop buying and hopefully they will find a way to bring costs down if that happens.
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