I missed the part where you specifically asked about less expensive options. I would not go to Vortex because ,at least when I was researching this topic a few years ago, none of their models are "constant on" which was a deal breaker for my purposes and they don't look durable at all although that is purely speculation.
The DP pro is decent but but only around $75-100 cheaper than an RMR and in my opinion the RMR is the most durable. It's only competition for durability is the Aimpoint ACRO but the ACRO cost even more than the RMR.
For a cost effective but reliable option I would go with the Holosun and not worry about it.
Side note, If its just for concealed carry then this isn't really needed but If this gun will see some abuse I would recommend an aftermarket adapter plate like the C&H precision plate. This would be much more durable than the standard MOS mount.