Okay somewhat bad news - the price history function is broke at the moment and won't be working again until this weekend. Turns out that there were so many server requests (which were subsequently timing out, because SteamGameSales.com is SLOOOOW) that my hosting company suspended my account without warning.
After battling with them on the phone for an hour last night, they finally agreed to re-instate my hosting if I agreed to remove the offending script. So now, every price history request will return "No Information is available."
I'm at a professional conference until Friday, but I'm hoping that I'll be able to set up something this weekend.
Wow that sucks. Sorry to hear that.
Here's my thoughts on the situation:
Why not just put a link up to that says "Click here to check pricing history on Steamgamesales.com". Since you can basically take any game's url of steampowered.com/app/<APP #>/ and change it to steamgamesales.com/app/<App #> and you have a direct link to the page on that specific game with pricing history.
It's only one more click and you actually get some more detailed info like the graph. To me that's more helpful than knowing something was $2.50 at one point. It doesn't tell me if that was a one off or if it goes that price at lot and thus will be likely to do so again.
Also it solves the whole currency thing because people can just set Steamgamesales.com to whatever their region is.
You can also do it with steamprices.com but there it's slightly trickier. It goes from steampowered.com/app/<APP #>/ and change it to steamprices.com/<region>/app/<App #>, so for the US it would be steamprices.com/us/app/<App #>. You could still do it but it would either default to US or you could maybe set something up in the settings so that people can specify their region.
Anyway, I think the link solves the issue of your plugin pulling in extra data and queries while still giving a convenience feature. It's still a lot easier for me to click a direct link on a page than to go to Steamgamesales.com and deal with their heinously slow search to find the specific game page I want or to manually type in the url.