I've been pondering this question of "investment grade" for a few hours,
I guess it depends on what level you are investing I'd say.
If you are looking for immediate returns only mispriced items should
be bought, and sold shortly thereafter.
If you are looking for long term appreciation of value there are two avenues, that can be combined.
One is to buy pieces from well established artists, preferrably popular in several markets.
With the expectation that the piece will appreciate nicely in value over the period you own it.
This usually means high-end items well above the four digit mark.
The other is to collect pieces from new and emerging artists in the hope that they will become popular,
usually less cash intensive but with a higher risk involved.
Both strategies are long term/deep pocket.
In the business world investment grade usually means something that you
expect will appreciate niecly over the years with a low risk of major loss.
One thing I have learned is that signature of well known artist = higher price.
Sometimes a very significant higher price. Same with unique vs serial.
For me the most important thing when buying glass is that I like it,
it will look good in my collection and it isn't overpriced.
I try to find pieces that are underpriced or that I think may appreciate some in value,
but I won't let a piece I want go just because it's priced at market value.
I hope my collection will appreciate in value,
but even if it doesn't it has value to me both as objects of art and being useful.
Your piece is beautiful and well worth the price, will it appreciate in value over the years above inflation?
I don't know. Is it signed?
If it is by Luigi Onesto then he's an established artist who commands
fair prices. From what I found he started out in the 60'ies. An Onesto sale on Ebay
This one is either not unique or has been sold several times on ebay.