Wow, Rob, some very cool oddball stuff! I can't help with the modern or games but IV I've seen those mats (large) go for between £3-£5 each. Personally I would only pay £3 each but I'm sure there's others who aren't so tight. I guess the smaller ones would be £2-£3 each.
The Jabba bits are probably £8 all together (no shortage of bagged bits available), the DCs vary between £6 for the incomplete Slave I to £12-£14 for the Cloud Car. They seem to be common enough complete. Shame about Tie Fighter and Slave I as they're the last two I need (ignoring Tie Bomber for now!)