A 2002 TB20GT (i.e. one of the last ones made and IMHO the best) seems to fetch £140k or so even today. I have this verified over several sales where I happen to know the background (most people lie about how how much they lost on a sale). One went for quite a bit more but it had TKS and a load of other gear. That is a depreciation of say 25% over 9/10 years, give or take the cost of avionics and other installs.
A 2002 SR22 will have lost a lot more than 25%. Probably closer to 50%. But the reason for this is obvious to me: Cirrus keep churning out new and "better" models, and in this market segment (if you have £200k you probably have £300k, but you probably won't have £1M) this leads to a substantial loss of sales value. This in turn makes an older SR22 good value.
I don't think an SR22 will drop as quick as a top end car. The dep on those is massive. My 1995 Toyota import was about £50k new (in Japan) and is now worth about £2k.
Old TB20s, say 1985, go for £40k but they tend to look the part. Prices in that market (old IFR tourers) have recently taken a big hit.
One SR22 I know of is renting at about £250/hr, which is pretty steep, but having been in that game briefly myself I can see why. They have opened it up to anybody with a PPL, and being a business they have to work the full depreciation into it too.