Shipping/receiving-fag here. I'm not a math-whiz, but logic can get us started on a hypothetical here:

First, let's think of how many shipping containers are on this one cargo ship. These ships max out at about 21,000 TEU's (which are size units. One 20-foot long shipping container is a TEU. The more common size, 40-foot long containers, are 2 TEU's) So let's presume that each of these ships is at just under 3/4 capacity, hauling 15,000 TEU's.

The maximum allowable net weight (the weight of the contents, but not the container itself) of a TEU is 47,770 pounds. Granted, it is not likely that every container is full to the brim, but knowing how import/export goes, and the costs associated with the transport itself, you could assume that these are likely loaded towards max weight, or capacity (some things can fill the containers physical space without reaching its weight capacity) This can't be estimated accurately for the entire cargo ship, since we don't know the contents of these containers, but this gives you an idea just how much one container could be holding. Personally, every shipping container I've ever seen come and go which was traveling overseas was made damn sure to maximize as much as we could fit onto it.

Let's assume that each container on these ships is meagerly holding only half of it's potential weight capacity, at about 24,000 pounds per container.

Now let's look at how many ships are actually passing through this Suez Canal on a daily basis. Just over 18,000 ships per year pass through here, which divides down to about 50 cargo ships per day.

15k TEU's, multiplied by 24,000 pounds, multiplied by 50 cargo ships, and we can estimate that there are 18 billion pounds of goods passing through this port daily.

If we assume they're all maxed, we would get 21k TEU's by 47k pounds by 50 cargo ships, for over 49 billion pounds travelling in and out.

It isn't easy to calculate exactly how many dollars are in play here, since some goods cost multiple dollars per pound, while others cost less than a dollar per pound. I'll leave it to your imagination as I make my final point:

The crux of all of these materials being halted in transport like this is that many businesses and industries will need these goods in a time-sensitive manner in order to satisfy their production needs. Some factories will likely halt production while they await materials. Manufacturing lines will go silent and wait. Many customers will get the second-hand shaft of this. Chances are, these manufacturing companies have already been commissioned to make the vital goods, and have likely promised that they would be finished and delivered on time to their customers. Usually, even a one or two day delay can spell disaster for the production of essential goods (food, medical, industry, etc). A common occurrence in manufacturing/shipping is an "expedite", which basically means it was either produced too slow, or is in such high demand by the customer, that it will now circumvent typical shipping routes and be delivered directly from the manufacturer to the customer ASAP (think truckers driving vans on the freeways, think cargo airplanes jetting across the skies). These "expedites" alone cost BIG money, and yet also the production downtime must be factored into the total cost associated.

In closing (and i hope i haven't been too superfluous) this will likely be a MAJOR COST economically for all involved. Workers may get layed-off for a bit. Businesses may close their doors... Geographically, it is interesting that it involves China and the Middle East. Whether this blockage is intentional or accidental, it will likely have major impacts.