What do you mean?
It is wayy cheaper to use 1 UTXO on 1 adress than to have 10 UTXO's on 10 different adresses.
Transactions will be significantly cheaper, especially if you're using low amounts (dust).
Why do most wallets recommend creating a new address for a new transaction?
They create new a new address each time because of 'privacy' reasons.
Since it doesn't matter whether you have several UTXO's 'laying on' 1 address or 10.
The size of a transaction is depending on the amount of UTXO's, not on the amount of 'input addresses' of a TX.
Edit: To slow.. but yeah.. I suggest reading this: https://en.bitcoin.it/wiki/Transaction#Input to understand how TX's work.
The picture at the right side explains it quite descriptive.