Concept - some one needs to get paid for doing their job of making concepts.
Computers and CAD (and CAD updates) - since GW uses computer aided drafting programs, they need comps and CAD programs (which are pricey)
Molds - you must make molds
Pewter and plastic - plastics and pewter has increased. also GW is now using a new better plastic then what they used two years ago.
Packaging - must package the figs
Gas prices increasing - increase prices of shipping due to gas have increased prices.
Advertisement- gotta advertise...
Yes, but this is true in anything.
See above (not necessarily the same equipment, but research is constantly being done for any company).
Molds are a part of the process of making the models and have been a static cost that wouldn't increase beyond inflation rates and this extra cost is applied each time they buy a new mold, not constantly.
Personally, I prefer the older plastic as the new stuff doesn't work so well with plastic cement nor if you don't bother to undercoat it first. I agreed with the tin though ;)
Packaging prices can be reduced by not using the cellaphane wrap on the boxes (of which not all of them have anyway) and not using the plastic compartment trays inside the box. However, packaging hasn't risen in cost beyond rate of inflation either.
Petrol price increases, most of this is due to taxation and in most countries, there is a SLIGHT reduction (not noteworthy IMO) for businesses. However, I do agree here still.
Advertisement? We pay £4 for their advertisement. At the moment, the only other advertisement they get is word of mouth/internet and from their games, which we pay for as well. (Yes, WD isn't a cost-free venture, but they still make a profit from it and we pay for the advertisements within it.)
Overall, they have had to increase prices due to tin increases, which would be felt elsewhere in other markets. Plastic has slightly risen in cost also, but again, this is felt elsewhere in other markets and lastkly, fuel prices are being flet across the board. Their price increases are beyond the rates of inflation and beyond the "add-on" cost increases of other things. they are raising prices in an attempt to make up for profit lost from LotR no longer doing so well.
Ultimately, it seems like this is just about working for them, but if they continue to do it, they shall quickly start to lose total revenue. With fixed costs as high as theirs, losing out on units sold is not good in the slightest as even a small drop (at the revenue they would've received instead) can be dangerous to them.
That said, it seems they may be changing their minds with the plastic cold one riders. The current common example is the two extremes of cold one knights and blood knights with a price difference of £28 due to the blood knights being metal (however, these will have less spare parts and, IMO, aren't as detailed or well done). Even so, a box of Chaos Knights is (IIRR) £30 which is still £18 more than plastic equivalents... Now, the cost differences between pewter (and/or its components and processing) surely isn't representative of such cost differences?