One thing you need to take into account with those tech recruiters is that most of them spam that same job posting to everyone.
It's actually quite annoying as I keep getting PHP job offers recently when my linkedIn history shows I moved to C# two years ago, because they found the PHP keyword. Most of those job offers are "meh", as in either lower salary than I earn now or worse work, with very rare cases of earning more and better work, just because I already earn above average for experience, so they're pretty useless.
Most devs earn an okay salary, 30-40k within 5 years is nothing to write home about if e.g. Cape Town with degree in Software, you should earn that in <2 years as a dev if you're doing back-end or full-stack work. Note that's 20-30k net or so. That said, most of the time to hit that, you're doing quite a bit of overtime and are valued by the company. I know quite a few cases with devs earning 15-25k in their 5 years because they basically never left the first company they worked for and it's a cushy job since nothing expected of you in those (e.g. one person working for a car sales place, only dev, I earned more than he did after 3 years with just my starting salary, think he swapped jobs now or was in the process of doing so).
In order to earn that 30-40k+, most devs work quite a bit more than they should, most of us take all the problems home and are still thinking about work even outside of work hours, since we like our work. You also have to put in a lot of time to learn whatever tech stack and process the company has and try to stay up to date, it's a field that is constantly moving, with often having higher requirements in terms of logical thought process than most other jobs, so that salary again is not the greatest for what it is, and moving to e.g. Europe or US just jumps up your pay grade as South Africa basically never kept up with inflation for a good 10 years on dev job costs.
Most LinkedIn recruiters are garbage, they're trying to play the shotgun game of trying to get as many tech people to reply as possible and then get that month salary commission for them staying somewhere a year, since most devs cannot move in <2-3 years if over junior as looks really bad on CV, most larger projects for a lot of companies take 2-3 years just to get off the ground.