If you're gonna make a CO2 laser you may as well shoot for more power because the difference in cost of materials for a 100W tube vs a 25W tube is small. I've been wanting to build one myself but have been stuck trying to acquire suitable optics.
As for the cost, a lot depends on what you can scrounge. Also a home built laser is likely to be much more fiddly and unless you've built them before, you will probably be a lot better off buying a commercial tube if you want to put it to real use.
As for the cost, a lot depends on what you can scrounge. Also a home built laser is likely to be much more fiddly and unless you've built them before, you will probably be a lot better off buying a commercial tube if you want to put it to real use.