Is $22,000 to install Okna 800s window inserts a fair price?

I'm looking for some advice on a window replacement project in my current home, which I'll soon be converting to a rental property (my wife and I are expecting and need more space for the kid, so we bought a new home). The current house has really old but beautiful wood sash windows that use the counterweight pulley system. They may not be the originals but I think they must be 40 or 50 years old. These windows are single pane, double-hung, and I'm sure there's no insulation in the framing, so they're highly inefficient. I don't think the sills or jambs are rotten, but they're definitely worn. I'm debating between inserts and full frame replacement. I understand there's a lot more work with the full frame replacement, but I'm a little surprised it's more than double the cost of the inserts. I'm also wondering if the full frame replacement is worth the expense. I'm going to be renting this property out in the near-term, but could very well sell it in 5-10 years and wonder what ROI I'll get on an investment like this. I'm curious if folks have a perspective on whether the full frame replacement is worth it or if I should instead just go with new inserts. Thanks in advance for whatever counsel you can offer!