Of course the price per gallon would be lower without government taxes, but I am not so sure that they are the epicenter of price increases sans taxes. The government actually receives more than the oil companies per gallon IIRC. Prices go up mainly due to speculation and if you’re selling crude oil, the more speculation the better.China increasing demand greatly is a big factor as well.
So far this year, ExxonMobil has paid over 2.6 times as much in taxes as their net profits.
ExxonMobil's third quarter results:
http://exxonmobil.com/corporate/files/corporate/investor_earnings_3q07.pdf
The government is always the “center” of higher prices for almost every item or product or service you (we) buy. Taxes play only a very small part.
China may need more oil than it once did, but the price is not going up for that reason. It is going up because the supply is being limited by government.