Well, it depends on the technology (is not the same Networking, IT Security than Technical Support), your formal education, if you hold any certifications, the companies were you worked and the real work experience on those 15+ years (if not anyone older than 40 should be considered a guru).
Check this site (
http://www.encuestasit.com/inicio), it will give you an idea based on the position. Besides that, any senior position will pay you minimun 8k net per month.