How to address PPP when doing price comparison across countries? I'm measuring some very specific items (across 5 countries) using my country's currency as the base. My questions are:


How should I address PPP in this case? (Is it just like the example in Table 1 here?)
What are the limitations if I decided to just use the market exchange rate? Is it considered "fair"?
As you are interested in very specific items, using an aggregate PPP measure like the ones provided by the World Bank (which are as aggregate as the GDP or private consumption), or the Big Mac index is not very good idea. This answer explains in some detail how PPPs are calculated ((the bottom line is that aggregate PPPs include a whole range of products; see here for more details).

If you are interested in just a few products, or maybe a single product (steel), as one of your comments suggest, you have to look into a more dissagregate PPP. You can find it here. These PPPs are still quite aggregate (for example, in the Classification tab you can find the full list). In your case, you might be interested in the Gross Fixed Capital Formation: Construction index. See here for more details on what this index includes. Notice that this is still quite an aggregate measure of PPP. Another drawback is that this is only available for either 2011 or 2005. 

A final note is that you are normally one adjusts for PPP when the interest is in comparing cost of living or wellbeing across countries. Adjusting for PPP makes less sense when the comparison is for example about the cost of sourcing a material from different countries. Here, exchange rates is what you need, as this reflects the actual cost for firms of selling/buying a product in different markets. As you do not provide the context of your question, it is not possible to tell whether PPP is pertinent or not to you.