Man it has been a while. However, the last quotes I had which was last winter are $4500 for Extreme and $2995 for Essentials. Since 3.51 was originally much more it might still be worth something, even though it is several years old. I would just consider the overall all price you are paying with upgrades and initial cost. If it is the same or less than the quotes I have, you got your money's worth. If you paid more, then well....
Hope this helps,
Urp