For those who do not know anything about tri wetsuits (i.e., NTPers), for the most part, the reason why one wetsuit is a lot lot more expensive (i.e., $99 vs $699) than another has to do with the materials. They type of rubber used determines the cost. The more expensive rubber, the more more flexible the wetsuit is ... hence more expensive it is.
If this is your first wetsuit, don't buy it online unless you've tried on the same size and model at a local store first. Those things can sqeeze blood out of a Vampire if the wrong size is chosen. Local stores that have wetsuits to try on include Contee and Bozai. Bonzai probably has the biggest selection in the area. You can also buy them or you can rent them at Contee and Bonzai.
Wetsuits are luxuries to have during the swim. If you are thinking about buying one, now might be the best time. Wait a few more months and you may have to pay a premium.