Some people who are Gedolei Torah are honored for it, and some are even paid for it. R may be saying that if you go into learning with the expectation of being treated this way, you will not be, and you will not succeed. Alternately, he may be saying that acquiring Torah cannot happen in one's spare time, while pursuing wealth and honor in some other employment. But that would be redundant with the previous statement. Could he be hinting to that someway over here.
R brings proof from rabbis mentioned in the Gemara.
If he felt so strongly about it maybe he wanted to bring it down here as well. So one might think that the Mishnah is telling us we can involve ourselves with Torah as well as wealth. This is what WILL happen - if you're ready to deal with it, you can do it, if not, you're in for a rude shock and you will fail. This isn't asceticism, but it is dedication. While Judaism does not renounce material comfort, it doesn't guarantee or glorify it either.