During the winter my local supermarket was selling this tent for around $7.50

http://direct.tesco.com/q/R.200-0497.aspx

It weighed in around 2.8 kg but if the fibre glass poles were replaced with some good quality alloy ones using a replacement alloy pole set for around $30 and the tent pegs replaced for 7075-T6 alloy pegs for around another $30 and the tent seems processed using a good seam sealer you would have a 2 man 2.5 kg tent with a 2-3 season rating i.e. the fly has a hydrostatic head of 1500mm, for around $70.

This tent would be pitched fly sheet first as well, which is useful for poor weather. This might be a low cost option.