This looks more about the IP blocks, which are probably similarly expensive from the competition.
The main Lattice Diamond SW is free, though again like the others you need to check which devices it supports and what other limitations there are with it.
If you do want to mess with Gbit ethernet, DDR3,PCIe etc. this looks like a very good deal (remember it's only a 1 year license though), though you may find that suitable devboards are fairly expensive.
ISTR Something that was fairly unique with Lattice was that it's the cheapest device that supports DDR3 wide enough to use commodity SODIMMs, which why David (Tesla500) chose it for the Chronos high-speed camera.