To add a little context, I joined a startup as a fullstack developer in late 2017, making me the fourth member of a team of two founders working sales, and me and a colleague doing the actual development of our platform. Upon joining, I got a 5% equity share of the company (now fully vested) in exchange for a ~$4k buy-in at ~$80k valuation. We've since then received a small investment of ~100k at a ~$1M valuation, and have scaled up our business but still only keeping it to our four member team.
The business has been good, and we're now about to close a pre-seed/seed round of ~200k at a ~$5M valuation to scale up and increase our team. This will be a first round that will be followed by another in a year or two.
I've had the exact same salary since I started, $3500/mo, without any raise. In the early days, we established a contract that would entitle me to bonuses if the sales were good enough over two consecutive months (which they've been) but costs has at the same time been too high to pay out any of my bonuses which I've foolishly accepted. I've brought this up lately, and only been told that we will look over the salaries "soon".
The two founders, both owning 25% each of the company, has had a salary of $2500/mo, but since the 2019 year it was decided that they would get a bump in their salary to $3500/mo, to support "their way of life". This was a decision made by them and the CTO.
All this has left me with the feeling of being undervalued and underpaid, given that my current salary is well below market salary. At the same time, I really blame myself for not speaking up sooner.
I don't know how to properly balance the equity vs salary equation, but I feel that their high number of shares in the company should argue for a lower salary on their part, and my low number of shares should argue for a higher salary. Is my way of thinking just wrong or even begrudging, and if so, what would be the correct way to view the balance of equity and salary?
Keeping in mind that we've worked closely together for more than three years which has made us good friends, if I should approach the founders with my concerns, how would I do so and what arguments would I use?