Worth going from R49 to R60 in attic

The simple answer is "yes". Every piece of insulation you put in is a bit of heat that's not lost to the outside world. This is better for you as your house is warmer and your fuel bills are lower, it's also better for the environment as you're not using as much energy.

The more complex answer is "it depends". Buying and installing the insulation costs money (you don't say!) so the immediate equation becomes "is this cost less than the money I'll save over X years?". It's the answer to this that will, largely, affect your decision on whether to insulate or not.

The company who wouldn't estimate may be right (for their system) in that it would cost $2,000 (say) to do the work, but you'd only be saving $20 a year on your heating. This would mean it would take 100 years to pay back the cost. Now, if you can find a system that costs less then the proposition becomes more economical. Insulating the ceiling/roof space is a good thing to do anyway.

However, if your primary concern isn't the savings then you might decide to go ahead regardless.

As with any answer, you should check your local codes. However, Going with R-30 on top and R-13 on the sides is standard and will give you very good value. If you can, you should plan on putting R-30 into the 'diagonals' too, that is, where the rafters are above the knee-walls but below the ceilings. If you don't have enough room now, you can screw some 2x4s onto the bottom of the rafters to gain more room: it'll be worth it in the end.

Two things to remember: you don't have to or want to insulate away from living space. So, from your diagram, you would insulate vertically up the knee walls, but don't insulate in the area you close off, as you won't gain any value from it. Two, make sure when you insulate the sloped area where the rafters are, make sure you put baffles underneath the plywood before you install the insulation, to leave space for air to flow from the soffit vents up to the ridge vent.