$28,000 for a level five trainer isn't too bad. You have to look at how much it will cost to replace him.
For example if a trainer cost $400,000 to replace.
If he cost you $20,000 the first week, then $21,000, then $22,000 etc, you can calculate the price point when replacing him is cheaper than leting his wages go up again and paying them again.
For example it can be clearly seen that at $60,000 a week you would save the cost of the trainer in just a few weeks ($40,000 saved per week means after 10 weeks you are ahead and making profit every week until the price starts creeping up).
But at $28,000 if you spent $400,000 to get a trainer with a $20,000 salary you would be saving $8,000 a week and it would take 50 weeks to make back your initial outlay, by which time you would have such high weekly wages that you should have already replaced him a couple more times.