I'm not a pro, but I am a breeder.
I agree with what has been said thus far. Different people have different ideas about what makes a high quality this-or-that, compared to a low quality this-or-that.
My high quality mojave for example, could be the ugliest mojave ever to you.
In general, what is desirable in pastels is first off high yellow coloring. This can be very hard to spot in hatchlings, but usually an orange hatchling is going to turn brown really quickly. I have however noticed a trend with certain pastels, they are orange as hatchlings and then turn yellow as they mature, but it is a lighter, brighter orange than a hatchling that will turn brown. It takes a great deal of practice to pick out the difference, which is why I'm still looking for my ideal pastel.
After the bright yellow coloring, the rest is subject to personal taste. One of my favorite pastel photos recently was of a stunning girl, very high yellow, tons of bright yellow blushing on her back, deep black side pattern, huge yellow belly flames, and a very small brown out line on her back. If I ever saw a girl like her for sale, I'd snatch her up so fast you'd think she was a mirage.
BUT, maybe your ideal pastel would be very high yellow and deep black, with little to no blushing and no flames on her belly. It's all relative.
Gale