Well, now, valuable and invaluable both mean of great monetary value, as do pricey and priceless.
But these apparent contradictions ar eonly apparent. If you understand the etymology involved they are easy enough to trace.
If something is tangled up in a random sort of way it is said to be raveled, and might have to be teased apart (unraveled) to then be properly and neatly knitted again.
If something is tangled in an orderly way, like a weave, the bits are tangled but in order -over and under and over. They are satill all wrapped up in each other, or tangled, and they can therefore be said also to be raveled, but more neatly. They can likewise be teased into an unraveled condition, with the strands separated out.