It depends on your requirements to be honest. So I'll pose some questions which may help mate.
Are you looking for the lightest bottle on the market?
Do you require a carbon fibre bottle or a steel bottle?
What size do you require (most people use a 1.1L in the tournament scene)?
Do you want new or second hand?
New prices for a carbon fibre bottle are around the £140 mark. Steel bottles retail for much less, around £40 mark. Second hand carbon fibre bottles in test and with plenty of life left are normally around the £80 mark