Trading value of Deep Songs vs. Ashur Tablets?

I'm giving up on Ashur Tablets (as I only have 6), but am in need of Deep Songs (I only have 2).

I did some searching on ebay and found:

• Deep Songs go for $20 - $25
• Ashur Tablets go for $37 (only one listing)

I made a simple comparison in a spreadsheet (see attached). Given an average of $ 22.50 for a Deep Song, an equitable exchange, for now, would be:

10 Deep Songs for 6 Ashur Tablets.

Would you consider this exchange reasonable? If not, what method would you propose?

If all you're going on is money then it seems about right.

10x DS x $20 = #200
6x AT x $37 = $222

As an example of what I value them at, I'll give you 6x Deep Song for 5x Ashur Tablets right now, if you want.