Hope you're doing great as usual. I'm on the jobs you assigned me recently. Here is something that I'd really appreciate if you consider.
I'm hope you're pleased with the articles I have written for you so far and quality would be my first concern in future too. I just wanted you to reconsider our writing rates. It'd be so kind and friendly of you if you can make it 1.5 cent per word and I'm sure my content quality deserves this little reward.
It's just a friendly request and it'd surely help me devote more time to your assignments and develop our business relationship better and stronger.
Thank you so much for being supportive and helpful customer throughout
Have a blessed weekend
Something like should work.