Hard to determine the value of blues

I am a noob when it comes to determine the value of magic items. For example, is this good, not bad, crap? I mean %300 ED is huge but other than that it has nothing than %amp. I know it would be op with +skillers. Same issue with jewels. %15iAs and %30ED is very valuable yes, but how about other jewels? Any guide or tips about these kind of items?

You can check the price of blue items price-check/howto-check-the-price-for-a ... 11135.html
You can also check if the 2 affixes can exist in yellow items. If yes then the blue one has no value.

This is partly why some blue/White/grey items can be so valuable, because nobody can tell and so nobody picks them up. I honestly don't pick up half the stuff I could, because I don't always know what to look for.

This is a decent starting point
https://maxroll.gg/d2/items/valuable-magic-items

It's really hard to determine. Sometimes I spent hours on a single item to find it's value out of desperation for high runes

Also, thank you @mockingbirdreal and @Knappogue for guide links