I wasn't about when they came out, so don't know what they cost then, but right now in the UK, the packs are: Mirage £3.49, Icarus £2.99, Harimau £2.99, Auricom £1.99, so yeah, overpriced IMO. I still bought them though (couldn't resist - it's Wipeout!). The Icarus pack is probably worth getting for TT at least.
The ships aren't usable online, but the tracks are (Orcus White is awesome!).
I agree about download games being not so good - if they were cheaper, then sure, but Wipeout Pure is £14.99 in the PSN Store, and around £10 in the shops for the UMD?!?!