I'm in charge in powdercoating in one of the manufacturing company in Selangor.

Usually, we do powdercoat in large volume for wiremesh, steel, aluminium. Since it is only 4 pcs of rims, expect a minimum of RM1200.00.

Also, I do know whether alloy rim is suitable or not to powdercoat, as the oven temperature is about 220 Celcius.

As long as there is a sample of the colour, the powder suppliers (Dupont, Jotun, Akzo Nobel,Orica) may able to mix, but not 100% of course.

Rm200 is quite impossible if using high quality industrial type outdoor grade powder.
Minimum 20kg of powder per box is about RM300.00. Then need to go through pretreament, labour, gas & water charges about RM300.00 for 2 hours estimated spraying time. Profit is 50% of the total cost. So, about 1.2K, unless you know insiders.