Bottle R contains 250 capsules and costs $6.25. Bottle T contains 130

When the numbers are this gross and the answers are orders of magnitude off from each other, we can estimate.

$6.25 = 625 cents. If a bottle of 250 pills costs 625 cents, each pill is between 2 and 3 cents. (as 250*2 = 500 and 250*3 = 750)
$2.99 = 299 cents. If a bottle of 130 pills costs 299 cents, each pill is between 2 and 3 cents. (as 130*2 = 260 and 130*3 = 390)

While we don't know the exact cost of each pill, we know that since both pills are between 2 and 3 cents, the difference between them must be less than 1 cent. E is the only answer small enough to be possible.

This process should take <30 seconds. Practice honing a sense for when the calculation you're doing/setting up is too hard to be realistic for the test and then refuse to do it — the GMAT isn't about busy work, so if the calculations are too painful, you aren't supposed to be doing them! Often the trick is another way of calculating, but in other cases, like this question, the trick is not calculating at all. A peek at the answer choices is often a good clue to whether or not estimation or a similar method will work: in this case, if the answers were closer together in magnitude, we would have had a much harder time estimating accurately.