If 15-20mgs of oxycodone will get you off, then probably 30-60mgs of morphine sulfate will do the trick.
The high is different though. Instead of being wonderfully euphoric, it's more of a slap you upside the head, really fucked up high. A lot of experienced opiate users tend to dislike morphine, but personally I like it. You're basically wrecked and end up sitting in one place for a few hours before passing out.
And $40 for 50 30mg pills is EXCELLENT. That's almost way too good to be true.
The only thing is you said "caps". I could be wrong, but as far as I know, pharmaceutical morphine intended for oral ingestion only comes in the form of pills. Again, I could be wrong.