Hi, you can use item variants to create options with different prices for an item. Variants will be available as selection on the product page, for example size selection here. You can create groups in variants configuration for width and height and fill them with options which will specify interval like the ones you wrote and then shopware will generate variants for each combination of them, for which one you will be able to set price and stock. If you require more complex configuration there is also a premium plugin which as far as I know allows to input exact sizes, you can check it on demoshop.
This custom item plugin doesnt have this option i have tried this. And variation option just work with defined numbers / measurements i need something in between if someone choose between any specific number like between 100 to 500 then price show the same.
i can see magento have a plugin for this here is the example solution which is i am looking in shopware. https://bit.ly/2L6Xmo7