He he .. I got started with less than 100 with my paysite
1. Content shoot by myself (sold it several times and gained back the money payed to models, so it costed me 0 USD)
2. Site made by myself : 0 usd
3. Processor with a little help from my friends .. also pretty little in USD.
4. Advertising in my other sites + signaturea in a lot of message boards .. also came cheap ..
5. Affiliate program will come pretty soon ..
so .. I guess that if you are determined to do it yourself can get it pretty cheap