With some Economy Fares the maximum combined Linear Length of any two pieces of checked baggage is 273cm/107in but no one piece may exceed a Linear Length of 158cm/62in - in which case the other piece may not exceed a Linear Length of 115cm/45in.
So for a 30 gram serving of protein it would cost about $1 per day. From these two samples of protein powder I found that an acceptable price range for 30 grams of protein from protein powder is between $1 and $1.50 (assuming close to equivalent protein powder quality).
Summary: Ranking of whey protein powders with the highest amounts of protein per serving. Just check out the nutritional information either on the protein supplement's website or check the back of your tub. The amount of protein per 100g (or per serving) should be near the top of the label. Some sites and tubs only show the numbers per serving instead of per 100g, which is annoying. If so, you'll need to do a bit of converting to get that easier-to-use per 100g amount.