How much does a Linux specialist/sys-admin earn as compared to a software professional ?

My Linux friends say that on average, Linux sys admins make 3/4 of what a top end software engineer would make.

Does it matter? The skill sets and habits of mind of a sysadmin are not the same as the skill sets and habits of mind of a software engineer; very few people are going to be equally competent at both. Don’t choose which one to pursue based on which one pays more in the abstract; choose which one to pursue based on which one suits you better, because a good sysadmin is likely to make more than a mediocre programmer.