Nice set! However, to be honest, I thought this was the norm rather than the exception.
Not sure how the notes came to be together. I take it you bought the notes and didn't find them yourself. However I've frequently seen X replacements available in groups that appear to be from the same sheet.
I have birds $2 EBX 3493496 and 3494996 (1500 apart) as well as $5 FNX 8314360 and 8315860 (1500 apart). I haven't seen too many 10,000 apart but I don't see why anyone would pay a premium for that any more than they would pay for notes that are 10 apart or 100 apart or 1000 apart.
On another note, I'm surprised you don't have 500 increments in your set since I thought those notes were skip numbered by 500 rather than 1000. Somehow you ended up with every second note in the sheet for some reason.