I did some quick calculations with the levels that had nothing in stock in my tower. I've provided the upgrade level as well as the total skills of the workers, and these all have three dream jobbers, but theoretically none of that should matter if we're only comparing relative values. This may not be perfectly accurate, as the "time" given to us might include rounding that isn't shown, but the general conclusions should be clear nonetheless:
Level Upgrade Skill Time Value Value per Minute
Mos Espa 4 26 22 2340 106.4
7 520 74.3
1 26 26
Ithorian 5 27 25 2520 100.8
18 1200 66.7
7 240 34.3
Ewok Sweets 6 27 29 3600 124.1
18 1500 83.3
3 150 50
Toydarian 3 24 22 2160 98.2
11 720 65.5
4 144 36
Pet Emp. 2 22 46 3960 86.1
23 1320 57.4
15 440 29.3
As you can see, the high-value item in each store generates credits more than twice as quickly as the low-value item, and often more than three times. This means that even if you spent all your time instantly restocking the low value item for as long as it would take to stock the high value one, you wouldn't make anywhere near as many credits. This holds true even if you have a dream jobber in the low-value but not in the high-value item. For that reason, it's usually a good rule to stock the highest-value thing first. However, note that if you have only two dream-jobbers, the mid-level item will likely be the most profitable (basically, just cut the high-level value per minute in half in the table above).
Occasionally it may make sense to optimize differently based on your knowledge of when you'll be playing. For example, if the Pet Emporium isn't stocked at all, and you're going to bed in 15 minutes, then stock the low-value one first, and get the high-value one stocking just as you're going to sleep. But that should be the exception and not the rule.