Yeah, the price tags on those kits are rather steep. You may want to get in touch with NIMIX by mail as they offer the kits at a lower price, expecialy if your currency is doing well against the Spanish currency. It is usually the Shipping and Handeling that is high (25% to ship to the USA!)
And there are many companies that have built the Vulcan. Academy makes the best plastic kit, for around US$32. Italeri also did a M163, but it is not as good. In resin, there is a conversion from Verlinden for the IDF version, and of course the Hobby fan one.
Also, another company, I am not sure, did a Vulcan on a pull-behind trailer.
And I have seen your work on other websites before...very nicely done. As I am sure most tell you, some of the items you have are rather "interesting", but for the most, you have an excellent grasp of "what may be".