SHA-256 is used to mine Bitcoins (BTC) and Bitcoin Cash (BCH). This means, that the only factor which influences the income is the mining difficulty. You can see the difficulty growth chart here - link.
Scrypt is used to mine Litecoins (LTC) and Dogecoins (DOGE). This means, that there are 2 factor which influence the income - the difficulty of mining (chart - link);
SHA-256 and Scrypt contracts are also subject to daily maintenance + electricity fees (MEF) which are deducted from each payout. Currently the MEF is 0.0035 USD per 10 GH/s of SHA-256 and 0.01 USD per 1 MH/s of Scrypt.
Once the MEF is deducted from a payout, the remaining amount is considered your profit.
*BTC/USD exchange value also influences the MEF (chart - link).
ETHASH is used to mine Ethereum. As the payouts are provided in ETH, the only factor of influence is the difficulty of mining (chart - link).
X11 is used for mining DASH. The main factor influencing the income is the mining difficulty (chart - link).
ETHASH and X11 contracts are not subject to any additional fees.