Pay them market rates. I worked at a company that would give performance based raises to market rates. Its not infinite and I knew it would cap out but starting at a jr and doing sr level work and being brought up little by little in salary is the guaranteed way to lose talent. Keep their raises at market rates for their talent. You'll pay more, but you wont lose them, and you will have a sr level in no time that knows your business in an out. Why would they look for other employment you are already paying them what they'd expect, and if you aren't, they'd expect it the next time raises come around. I only left that company because of a geographic move. May even go back one day.