domain DallasTexas.io

reg fee probably. .io domains aren't really used for city sites and thus I don't think these domains hold much value. thats just my opinion though.

One word IO are mostly what is selling so far, if they were the single Cities or States name would be a better value.

If you are willing to do the work and search for and contact tech companies in those locations, you might find and enduser, yet I still feel they might not go for very much $xx

And for future reference 1&1 can be a difficult registrar to deal with, IO is $25 at Moniker and $32.88 at NameCheap

Inviting you to study and hang out in the IO thread, you'll learn lots there
https://www.namepros.com/threads/io-thread-and-showcase.848819/