Originally i didn't understand the need/desire
But I think if you add a DEC cost then sure why not... that would be my response.
I actually think it adds a benefit of helping new players get the exact amount of cards they need to get to the next level they're aiming for.
However it could have the impact of pushing prices down a bit because it could expand the number of singles... however on the other hand those singles have more value because of the burn cost ... so I'm not sure. There might need to be good enough demand for those 1bcx cards... right now I don't know if there's the demand so what good would it do us.

However I think the formula would probably need to be much more simple than requested.
Like one % burn price. I guess that could be based on burn value?

It's easy to know the burn value so you could do something with that number easily.

IN OTHER WORDS
It seems like the present system rewards users to NOT COMBINE because they know the 1bcx cards will be worth substantially more than uncombined.