I went to buy Standard Health Elixirs from the Esior's Haven Town Hall, and I selected to buy 5. When I hit "Purchase" the cost was NaN Coins. Slightly worried, I hit buy, thinking it wasn't going to be much of a problem and I could come report it afterwards. After buying it, I noticed I didn't lose any coins.

Did you receive what you bought? Or was the entire transaction null?

I got what I bought

Then it should have charged you, as that's determined server-side.

Basically, when you buy from a shop it posts the items you have selected. Then, server side, it checks to make sure those items exist and finds their prices in the database. Calculates, takes gold, and then adds the items.

NaN showing up as the price before you bought was just the javascript part breaking. NaN is the default basically for a null value after trying some type of numerical function - in this case trying to add a comma to the price.

Purchases from the old layout shops aren't tracked so I can't verify anything, but if you received the items, it should have charged you. NaN or not, that portion doesn't make a difference on what you actual pay.