Why is there a higher fee for re-used receiving addresses? Say I want to get lots of small bitcoin deposits and sell them off soon thereafter.  Say I get bitcoin in $5 chunks.  If I take the standard advice and never reuse an address, I have to pay a transaction fee every time I sell one of those chunks.  As of this writing, the average fee is over $2.  This puts the overall fee for this endeavor at 40%.  On the other hand, it seems like I could collect all of the deposits in one address and sell when I've reached some acceptable threshold, say $100.  It seems like this would cost me a mere 2%.

On the other hand, I have read the following at https://en.bitcoin.it/wiki/Address_reuse#High_Fees 


  A single invoice payment using P2PKH can be redeemed and spent with a predictable fee because the transaction should have a predictable size. Software that determines payment and available funds based on "address balance" can cause loss through high fees. If you are paid to an address in many small increments, you will pay a much higher transaction fee when redeeming those payments. It is much more useful for a client to display transaction outputs spendable than address balances for this reason.


My understanding was that transaction fees are per byte, and that my transaction would be a standard sized one of the form "MyAddress is sending x many Satoshi to YourAddress".  Why would I have to pay more?
When you have an address with multiple inputs (you have sent bitcoin to the same address multiple times) and you want to send all of those bitcoins to another address, all of those inputs must be included in the transaction, and recording each input takes up space. If you have only sent bitcoin to an address once, it only has one input, therefore the transaction only needs to contain one input, which takes up less space.