I believe most fancy serial number collectors (I am not one of them) collect small denomination bills. I believe it is mostly a practical matter. For example, if the premium on fancy serial number is $10, then a $1 bill costs $11 and a $100 bill costs $110. This is more the case with common fancy numbers (radars, repeaters). It is simply cheaper to collect the small denomination bills. Rarer fancy numbers (like solid numbers) are going to be collectible in any denomination. Does that help?