How to model that several variants of a merchandise item may affect its price? I am an absolute beginner to relational data modelling. I hope my question will be acceptable here nevertheless.

Let’s say there’s a merchandise. An item of merchandise may have variants.
(While it also has attributes common to all variants).
I don’t want to limit in the data model what the variants can be.
I know the merchandise can vary in size and in color, but I don’t want the model to be limited to these two possible variations. There might be other variants (such as in material or process).
It is not clothing, and the variants may be priced differently.
While I expect mostly sizes to affect the price, I don’t want to impose any such limit.I also wish to anticipate that several variants could combine to affect the final price. Say that a different process could affect the price and different sizes too but colors not. But I want to avoid any fixed limitations in the model.This is what I don’t know how to model properly.

(BTW, variants are identified as such by adding a variant code to the base of their SKU.)
If the variants are identified by a variant code at the base of their sku, is the variant code always in the same place?  If so, you can always group together with the base sku.  

However, you might want to look at product grouping.  As an example, if your catalog of products is exercise products.  And you have fitbits.  The Fitbit flex can be sold with different colored bands.  Each one would have a sku of 1234 with a letter variant.  So bl for black, bu for blue, pk for pink.  so 1234bl is black fitbit flex.  

Now you can set up categories.  So the next level would be the type of fit bit.  You also carry the fitibit Charge.  That sku is 2345.  So one item can have a sku of 1234bl, a subcategory of Fitbit, a category of pedometer, under the store area of technology.  And you can group the data at those various levels.  A vp of Electornics might only care about the Category and the technology level.  Yet a Category manager cares about the sub category and category.  They may also care at the sku level.  

Does this answer what you are looking for?