Prices are mainly determined by quality and production. If you are less concerned about the quality and origin of the tea, you can find one for little money in the supermarket.
You can also ask for advice in a tea shop and choose a more expensive variety. This decision is entirely up to you.
Many Earl Grey teas in the lower price category have artificial flavouring. These do not come close to the aroma of bergamot. They can be recognised by a very intense lemon flavour.
A high-quality Earl Grey is characterised by a fine taste and the special fragrance it gets from the bergamot fruit. High-quality teas are available from a medium price range.