I'll share with you everything I know about tungsten weights insert vs. no insert. Take it for what it's worth. I not only worked with manufacturers to develop my weights, but also work in the tool industry buying, selling, and grinding tungsten carbide.

Tungsten (carbide) is mined from the earth, and refined by grade and partice size. 95% of all raw tungsten comes from China. The tungsten powder is then combined with a binder material such as cobalt or nickle and cast into its raw form. The pliable form is then sintered in an oven at extremely high tempuratures to produce the finished product. Hardness is deturmined by not only the mix between the tungsten and the binder, but also by the tempurature and duration of the sintering process. Surface finish can not be guarranteed in this process and rough spots are common. It does not take much of an abrasion to fray fishing line.
I am not sure about all brands of weights, but I use PVC tubing which is very pliable and soft. It projects out the end and you can pinch it between your fingers and it returns to its shape. This insert will not harm line.

There is another process that involves honing the ID of the weight with a diamond polishing tool. I looked at a variety of sample weights treated with this process under 200X magnification, and deturmined the results to be inconsistent.

I did not want to risk abrassion for my own use, so decided to stick with the insert.

While tungsten is much more expensive than lead, the high prices we all paid in the beginning made a few people ALOT of money. We also paid for a lot of marketing and prostaff costs.
The price will continue to come down as more weights hit the market, but could be effected by raw material costs if demand from other uses increases.

Lower quality tungsten weights are made from recycled material and will be less dense and not as pure.

Be happy to answer anyone's questions.

I will no longer peg the TT weights because of the numbers of breakoffs I've had on hookset.