It actually depends on the steem power of the whale who intends to upvote your comment. A whale with a very huge steem power can give you an upvote worth more than $1. It also depends on how generous the whale is because some will set or filter the voting weight or worth by using busy in which they are able to set their voting percentage before Upvoting your post.
Most whales actually don't give 100% upvotes while some may give it out depending on how generous the whale seem to be. You may also be lucky to have a whale who may set your account on auto-upvote such that anytime you make posts on Steemit, you authorize get upvoted by the whale.
In conclusion, not everyone with huge steem power will give you an upvotes for commenting but if you actually get upvoted, the worth of the upvotes depends on the steem power of the weight and the percentage of upvote you receive from the whale.
Thanks for reading and I hope this helps.
Comments you said, well i don't think they add any impact, rather than the great feel of , oh!, a whale actually took time off their whaledom and commented on your post.
An upvote from a whale though, goes a loongg way. i personally can say my account "with the little i have achieved" is where it is because of one very awesome whale, @surpassinggoogle. so yess, upvotes do count, majorly.
This is a great question and something that has been debated for quite some time. When you are a new user starting out, it is really easy to find yourself chasing upvotes. That is the most obvious reward you can see. I wrote a post, it got upvoted for x amount, in seven days I will have x added to my wallet.
That first big upvote from a whale can be a real rush. Many times however, once you get that big upvote, you may never see anything from that account again. I had that happen quite frequently when I first started on here.
In contrast, if that high SP account actually leaves a comment on your post, that usually indicates that they actually took the time to read your post. Hopefully, it was a good comment and they saw something they liked. Having that happen will give you a much greater chance of them following you and reading your posts in the future. That will hopefully lead to more comments and more upvotes. Maybe even some resteems to their friends that also have high SP.
The short term impact from a comment by a high SP account certainly won't be as obvious as an upvote from them. The long term impact can be game changing for your account though. That is why many people say I would rather get good comments on my posts than upvotes. Those strong interactions lead to relationships and in turn upvotes that will eventually help your account grow.