Inverters aren't cheap especially if you want a good one that will allow you to run things for a long time or items which use more watts. Me & my mate used them in our mobile catering van when we used to run a small catering company together.
The inverters we used where around £500 each (still fairly cheap ones) and this allowed us to power a small fridge, panini press & microwave. Wish I could tell you more on the specs etc but it was my mate (business partner) who ordered them & was more electrically minded than me.