I started back in SLR photography last year with a Nikon D40x kit (on cashback) , Lowepro bag, spare batteries, SD cards, filters, ..., for about £550 all up.
I have added a Nikon 70-300 VR zoom lens at £300 since then.
Having had a very enjoyable year with it, and having looked at where I want to be with photography, I will probably add a D300 body and either the Nikon 300mm f/4, or the 300mm f/2.8 VR.
This will give a higher usable ISO, 6400 for the D300, compared to 1600 for the D40x. The prime 300mm f2.8 lens will give me more stops over the 70-300mm f/4.5-5.6 zoom, and better contrast/definition.
Motorosport and aviation are my main subjects, and the additional camera/lens combination opens up some possibilities that have been hard to cover with the existing kit.
The next year's spend could come to over £4000.
Edward