the older wavy glass looks quite different and nice. Just find an old building that has them and even from the street , just notice the reflection off them from nearby streetlights etc. right away you will see the waviness. You can get manufactured wavy glass , it might be a bit wavier and more imperfect.
the windows in my house 1924 are quite thin, probably 2 mil? If you buy new glass, since it's dead flat with no character anyway, you wont' see a difference if you use heavier glass. it will increase the weight of the sashes of course but also it stops more noise. you were getting misinformation about it breaking differently.
things like commercial doors and glass people put around porches and the side windows in cars are tempered glass and if that shatters it turns to a million bits to prevent it cutting people. this isn't used normally in houses, especially old houses, not for windows. tempered glass cant' be cut it has to be cut and then tempered after.
You can check with the companies that destroy old windows to replace with vinyl junk, maybe there you could check if there are some art glass places, look if someone specializes in stainded glass - ask them. I tried a couple places and they just trash then where I called, they have no respect for old buildings obviously. I think if you talk to the road crews that are out doing all the damage , they might save them if they think there is beer money in it.
If you are paying a lot for all new windows, and if you have place to work and an interest in woodwork I think you could look at some used machines and tools to make your own windows. I'd prefer to buy the tools and use them and maybe sell them down the road as opposed to paying thousands for windows. the pricing sounds very extreme. you could watch some Utube videos on making windows to see if maybe that is something you could master if you are so inclined. you can make them with a tablesaw router and jointer and your technique may vary depending on your machinery. You can buy your own CNC router table for $2700 Canadian and make all sorts of things. You need to consider how loud these machines are but you can do a lot of neat things with a CNC router table! There is a lot of used and somewhat antiquated machinery on the market and some is less practical for industry and beautiful for the homeowner that wants to tinker.
here's an industrial shaper in calgary just as an example.this one is $2700. you could probably find them cheaper. its basically like a big router. the cutterhead in the middle of the table holds the special knives used to make the profile of your choice.
https://www.kijiji.ca/v-power-tool/calg ... nFlag=true With a decent tablesaw, a 6 inch jointer, and a shaper and some sort of dust collector you could be pretty much set up and them make as many as you want , but with a learning curve of course. you could have that for under 5K with a little shopping. compare that though to spending upwards of 20K on windows. you can sell the machines for what you paid if you shop wisely.
I'd consider making windows a fairly advanced woodworking project but I just wanted to point out that it is possible. So much is going to CNC now that some of these older machines get replaced by newer technology. If you watch for auctions of government assets and woodworking equipment there are some super deals out there. If that sort of thing didn't' suit you maybe it would suit someone you know. you would need to be prepared to practice and just try making them from pine and expect some errors in your first few tries but if you get into it you can do this without being a brain surgeon. so for example if you know someone with a flair for woodworking maybe you could work something out.
Some industrial machines are 3 phase and you wont; have 3 phase at home but you can buy phase inverters quite cheaply nowadays. they convert the household power to enable 3 phase equipment to run on 220 single phase which you will have at home. on some machines you can change the motor , on others the motor is special to the machine and you might need a phase inverter to run it at home. You may also find industrial quality shapers and tablesaws that will run on 220 and not need a phase inverter.
if you have windows that used rpes you will probably see where they were attached to the edges of the sashes. Yes it is possible the sashes were never fitted with weights but in most houses they were. some had pockets accessible through the window frames , others you remove the side casings to access them. you cna probably add the weights provided you have the pockets for them to hang in. some also had a spring loaded recoil device that would do similar only without the use of weights.