Many thanks to all those who provided helpful suggestions, even those who ignored the $200 limit :-)
To summarize:
1) Hacksaw with a lower tooth count - agreed wholeheartedly! Would you believe that on the day in question there was no blade with less than 18 tpi in town? I have since learned to hoard consumables. Also agree that for more than an occasional cut this would get very old very quickly.
2) Abrasive disk - with many reservations but costwise very attractive: One can often pick up old circular saws in garage sales and dedicate them to this job.
3) Tenryu or similar blade. This piqued my interest. I e-mailed one of the dealers. The Tenryu site was not exactly clear what kind of thickness these blades can cope with - many were listed with outright limits such as 1/8" or
1/4". I am not sure that I got a clear answer but the implication was that the right sort of blade would cut in a circular saw up to 1" thickness without a worm drive. I shall look into this further.
4) Porta-band - although the method of making 8" cuts in a plate remains unclear. I shall probably get one just for the hell of it and because I have not bought a major tool for at least two weeks.
5) Stationary band saw if you live in the USA. Nothing here under $300.
I am eternally grateful that I live in the age of the internet and have access to this group.