I've had the ProStaff 4x32, the Buckmaster4x40, and a old (before the re-design last year) Monarch 2-7x32. Honestly, I liked all three scopes pretty well. When you compare them to other scopes in their respective price class, they are all very competitive.
I paid $89 for the Prostaff and had it on a T/C Black Diamond, and it's probably the best glass I've looked through for under $100.
I paid $149 for the Buckmaster and put in on a T/C Omega Z5. I really liked the adjustment knobs on it, easy to grip and precise, without the need for any tools to adjust them. Glass was great. My only objection to it is that I felt that it was just a tad too long for a 4x fixed power scope at 13+". Again, for $150 or less, probably the best glass I've seen.
I paid $250 for the Monarch (that was at least 10 years ago). Superb glass, IMO, perfect size and weight. Eye relief was good too. For some reason the power ring was very stiff, and it didn't loosen up with use. Not a problem, really, as I usually kept it at 4x. It was on a Remington 700 stainless Mountain Rifle in 30-06. That gun kicked pretty good, especially with the 180gr loads, but the scope never failed and I never got bit by it either. When I was shopping for a scope on this gun, I spent hours looking at virtually every scope that cost OVER $250...Leupold Vari X II and III, Zeiss Conquest, Elite 4200, etc. I thought that the Zeiss was the best, but $500 was a little too high for me. Out of all the others, I liked the Monarch WAY better than the rest of them. No contest really.
I haven't looked at the new Monarchs, but I'm sure that they are fabulous.