If you had the knowledge and access to the proper tools, you could build yourself a custom guitar for $600 or so depending on a number of things; woods, electronics, aesthetics. For someone reputable to build you a guitar would easily run you thousands of dollars.
An archtop however will cost much more since it requires much more time, effort and skill to build. A true arch top is hand carved on the inside and outside of both the top and the back, which believe me takes a shit load of time (pictures below of my work in progress, read: 3 years in the making.)
There are plenty of companies out there producing affordable hollowbody/semi-hollowbody guitars. Depending on the versatility and the overall tone you are seeking, will ultimately determine which brand/guitar is for you. The best advice that I can give you is to head to the local guitar shops or even drive to some farther ones if need be and play as many guitars as you can with a similar amp as your own. Once you play a few, you will know what you like and don't like and will be able to pinpoint the perfect guitar for you.
I've included a few pictures of my small guitar collection. I have built a few instruments and have a few still in the making. I do not have access to tools and most of my wood/supplies are 1700 miles away.
Custom Slope Shoulder Dreadnaught: AAA Flamed Koa back,sides and rosette. Pillow Top Sitka Spruce Top. Ebony Fingerboard and bridge. Flamed Maple body and neck binding, and a 3 piece Honduran Mahogany/Flamed Maple Neck.
1971 Harmony Folk, Custom Electric in progress. 2" Solid Honduran Mahogany with AAA Flamed Koa top and back (exact duplicates from same tree), this guitar will have a set neck and stop-tail bridge, dual humbuckers with dual tone/volume controls and coil tapping with a Fender neck/scale length. The body alone already weighs as much as a Les Paul. The body is taken from a Strat, but modified slightly. The headstock is also modified from a 60-70's large headstock. And finally my jazz hollowbody in progress. European Maple back, sides and 5 piece neck with an Englemann Spruce top. Rather than taking the typical approach with F-holes I opted for a bassier tone with a sound hole from a 1930's Gibson.
I also have a few more, my custom acoustic from above and my two electrics. 2001 Gibson Les Paul Standard Double Cutaway Plus. This semi-hollow guitar has more sustain than any other Gibson I've plugged in. And my 1996 50th Anniversary Fender Standard Stratocaster, (Fender's 50th Annivesary, Not 50th Anniversary Strat.)
I realize this is a lot of bullshit in here, but when guitar threads come up I salivate a bit. I did go to school for guitar repair and construction and have a degree in guitar repair. I highly recommend checking out some schools for it, it is well worth it. Building your own custom guitars to your specs with someone else's tools...very handy when you can't afford the necessary tools. However the hand tools/supplies needed for school alone exceeded $5,000 so know full well it's an investment, that does not include the materials and parts needed for guitar construction.
Hope this rant helps.
